asterisk users - Feb 2014 - Polycom does not register from outside to asterisk

Hello;

I have asterisk?Asterisk 1.8.23.0-vici and Polycom 331 and I am able to register
from local area network and not able to register from outside the office. Also
from outside the office, I am able to register via PhonerLite softphone and not
able to register via Zoiper softphone.

So from outside the office, I am not able to register from Zoiper softphone and
not able to register from Polycom 331.?

I set the externip to the router real IP address.
Also, I set nat=yes.

What could be the problem? Why I am able to register from outside the office
using Phoner Lite softphone and not able using zoiper softphone or Polycom 331?

Is there anything special settings that can resolve this problem?

Regards
Bilal
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