Unfortunately, many people don't realize it doesn't matter whether they've changed anything and whether something has worked fine in the past. Several things can happen without someone changing anything, and one of them is a corrupted NAT association developing between a router and an ATA. Another is getting hacked. And yet another is running into temporary IP bans. And then there are hardware failures. Those are all potential problems just off the top of my head.
The "check telephone line error" means that a telephone cable is loose or has become defective; your ATA's phone jack has become defective; or your ATA isn't registered for whatever reason. In other words, the telephone isn't receiving a dial tone.
1) What brand and model modem are you using?
2) What brand and model router are you using?
Typically it's best to have your own router and to shove whatever modem/router combo your ISP gave you into bridge mode. If your ISP did give you a modem/router combo and you don't have you own router, ensure that SIP ALG is disabled in it. Otherwise you may need to use voip4.freephoneline.ca:6060 to circumvent buggy SIP ALG features. In your own router, you may also need to disable SIP ALG.
To understand why SIP ALG often causes horrible problems, please visit
http://www.voip-info.org/wiki/view/Routers+SIP+ALG (scroll down to the section on SIP ALG problems).
If you're dealing with a modem/router combo issued by an ISP or a router with SIP ALG forced on (with no way to disable it), you may have
to use voip4.freephoneline.ca:6060 for the Proxy Server. The purpose of voip4.freephoneline.ca:6060 is to circumvent
faulty SIP ALG features in routers.
3) What does registration status indicate after logging in at
https://www.freephoneline.ca/showSipSettings?
Also what doe SIP user agent indicate? If you ever see something that you don't recognize listed under SIP user agent, you've been hacked.
While you're logged in you might as well double check your SIP Username and Password against what you've entered in your ATA. They should be the same.
Be careful not to copy and paste empty spaces.
4) What does registration state indicate in the ATA after logging in under Info-->Line (FPL)-->Registration State?
5) What do the LED lights on your ATA indicate?
Power light should be blue. If it's red, you've running into some sort of hardware malfunction. There are also tons of fake PAP2s, and the fakes are known to develop issues:
https://www.ukvoipforums.com/viewtopic.php?t=565.
If the Phone LEDs are not lit, then the ATA has no registration.
6) Note that only one registration per FPL account is allowed at any time. When there are multiple devices/softphones using the same account, only the most recent registration is valid. The previous device will lose registration. This is especially important to consider if someone else is using your SIP credentials (username and password) that are found after logging in at
https://www.freephoneline.ca/showSipSettings (or if you're trying to register your FPL account with a smartphone SIP app or with another device). Registration is required for incoming calls. It is not required for outgoing calls. If you simply want to make outgoing calls using your FPL number, configure, but don't register the account, on the SIP app being used, with Groundwire, for example, on a smartphone (there is no way to do this with the Freephoneline desktop application; the Freephoneline desktop application doesn't offer to option to not register). This is also important to consider if you're using Freephoneline's desktop application (don't have it running while using your ATA with the same FPL account). Additionally, keep in mind that if someone else is also attempting to register the same SIP credentials on another device where you live, too many registration attempts can result in a temporary IP ban. Always check registration status in the ATA and also your SIP status after logging in at
https://www.freephoneline.ca/showSipSettings. If you see a device listed under SIP User Agent that you don't recognize, you've either been hacked or someone else is using your Freephoneline SIP username and SIP Password.
Each time you reboot the ATA, it's attempting to register with Freephoneline again. If you attempt more than 10 registrations in 5 minutes (this is why the registration interval is important),
you may end up being temporarily IP banned by the specific FPL server the ATA (and/or desktop app) was sending
registration requests to. If you're temporarily IP banned, you could then try switching Proxy to a different FPL server than the one you were previously using (voip.freephoneline.ca, voip2.freephoneline.ca, or voip4.freephoneline.ca:6060), unless you need to use voip4.freephoneline.ca:6060 because you have SIP ALG forced on in your router. The purpose of
voip4.freephoneline.ca:6060 is to circumvent SIP ALG features in routers.
https://community.freepbx.org/t/trunk-s ... ca/22479/8
"As May 2013, our servers will rate limit REGISTER requests to a maximum of 10 requests per 5 minutes. Each authentication round usually consumes 2 requests (digest auth), so it is a fair number given our guidelines. Also, it does not affect INVITES (which are also authenticated)…
This rate limit is applied per IP address as our service is tailored to residential Canadian users (ADSL/Cable)."
That's why the registration interval of 3600 seconds and failed retry timer of 120s in the ATA are important.
7) In your Line Tab (for FPL) in your ATA,
a)Register expires should be 3600 seconds
b) NAT Keep Alive Enabled should be Yes
c) NAT Mapping Enabled should be Yes
8) In your SIP tab in your ATA, under NAT Support Parameter, NAT Keep Alive Intvl should be 20 seconds.
9) Navigate to Voice-->SIP-->SIP Timer Values (sec)
a)Reg Retry Intvl should be 120 seconds
Mango suggests the SIP T1 default setting is too aggressive, and to help resolve potential registration issues, T1 should be set to 1.
b) Change SIP T1 to 1
10) In your ATA, Navigate to Voice-->Line 1 (or whatever you're using for FPL)-->SIP settings, change SIP Port to a random number between 30000 and 60000. Just pick a new number if that range. Save settings.
For security reasons, it's better to choose a local SIP port in this range regardless.
If changing the local SIP port works, you were dealing with a corrupted NAT connection in your router.
Possibly a NAT router connection was never disconnected or never timed out properly. And, then, the
ATA keeps the corrupted connection in a persistent state over and over again. (Credit goes to Mango for
this information). Possibly, this problem is due to the router's UDP timeout being in excess of the ATA's
Failure Retry timer. With FPL, that's 120 seconds.
Thanks to Mango, many of us now understand that in order for ATAs to remain registered and working
properly with a VoIP SIP provider like Freephoneline, in particular after power failures, the following
conditions must be met:
UDP Unreplied Timeout (in your router) < NAT Keep-alive Interval (in your ATA) < UDP Assured Timeout (in your router) < SIP Registration Failure Retry
Wait Time
“<“ means less than.
When a modem leases a new IP address, a problem can arise where prior associations using the old IP
address are maintained in the router. When the ATA attempts to communicate using the old IP address,
the response is unreplied, and then if the UDP Unreplied timeout is greater than the Keep Alive Interval
(and UDP Unreplied timeout is often set to 30 by default in consumer routers) a problem arises where
the corrupted connection persists. If UDP Unreplied timeout is, for example, 17, and the NAT Keep
Alive Interval is 20, then the corrupted connection will timeout or close. A new connection will be
created, and everything will work fine.
Another problem can occur when the Keep-Alive interval is greater than UDP Assured Timeout (often
180 by default in consumer routers): the NAT hole will close due to the ATA not communicating
frequently enough with the SIP server. In turn, incoming calls may, intermittently, not reach the ATA.
Again, NAT Keep Aliver interval is supposed to be 20 seconds with FPL.
Getting access to both UDP Unreplied Timeout and UDP Assured Timeout settings in consumer routers
may be difficult, if not impossible. Asuswrt-Merlin (
https://asuswrt.lostrealm.ca/about), third party firmware for certain Asus routers, does offer
easy access to these two settings, which are found under Tools-->Other settings. However, my
understanding is that third party Tomato firmware has these two settings as well. Mikrotik routers do as
well:
https://forums.redflagdeals.com/recomme ... #p28056619. If your
router supports Tomato firmware, that may be another option. Note that I will not be held accountable
any damage resulting from failed firmware updates.
The keep alive interval for FPL is 20. The SIP Registration Failure Retry Wait Time is 120. I use 17 for
UDP Unreplied Timeout and 117 for UDP Assured Timeout.
11) Your setup PDF guide is found here:
http://forum.fongo.com/viewtopic.php?f=15&t=16294. You may want to double check your settings (the ones I've specified here are correct if there are any discrepancies in the guide, such as local SIP Port).
12) Proper device boot order is always modem (wait for it to be fully up and running)–>router (wait for it to be fully up and transmitting data with Wi-Fi SSIDs populated first)–>and finally ATA (in that order). You can try rebooting devices now (wait for each device to be fully up and running before rebooting or turning on the next device).