Outgoing call problem - W52P

[GeorgeatSalem]

Problem: Yealink W52P can receive incoming calls but cannot place outgoing calls.

When I try to dial the extension of another phone on the network, ext 1050, I receive the error:

"Via SLS WiFi2
1050
Not Available!"

If I change the default outgoing line to the same as the incoming default, I get the same message as before, but with "SLS WiFi2" replaced with "locext1507".

All accounts are active and registered. Number Assignment looks right to me, but I could be wrong.

Any help would be greatly appreciated.

Thanks!