call forwarding not working with pstn number

[dcondense]

the call forwarding feature is not working with regular pstn number.

if the followme number is a regular phone. then there is a problem.

if somebody call FPL number from a regular phone, they just get either busy signal or occasionally the voice mail when there is nobody using FPL at that time.

but, it seems works with other FPL number, let us say, if somebody make a call from other FPL number, it will forward to the followme number.

this problem should be universal.

either the problem with server or networking.

please fix this.