Analog Intercom/Buzzer stops working with VoIP – Future Nine [fixed]

Quick post here regarding my Voice over IP provider, Future Nine, and theĀ Analog Intercom/Buzzer at the front gate of my community. When someone dials-in from the main gate, I need to pick up the phone and press 9 to open it. It has not been working as of late, and the only way to circumvent the challenge was to reset the Linksys VoIP box. It would last a few minutes.

My current internet provider is AT&T U-Verse. The VoIP box is plugged directly to the U-Verse gateway.

Future Nine replied to my concerned and suggested to make these changes under the advanced tab (LAN port, default gateway IP –

SIP Port: 15060

I am currently testing the changes, and will update with results in the next few days.

Update 02/22:

The service is now working properly. It seems that AT&T blocks port 5060 for their own VoIP service.