Calls end at 32 seconds

[Eagle2469]

3CX Professional 16.0.982
Polycom VVX500 - firmware 5.6.0.1735

3CX server is hosted in cloud on Vultr VPS.
Office is using Ubiquiti network equipment. DHCP server has TFTP for phones to auto provision.
Office has a Raspberry Pi running latest Rasbian and 3CX SBC pointed to 3CX server.
Phones are using SBC with IP address and router is port forwarding UDP and TCP port 5090 to Raspberry Pi.
SIP ALG is disabled.

No matter what calls are made, they always drop at 32 seconds. They can be ext to ext calls, incoming external calls, or outgoing external calls.

[CM503021]: Call(C:3): ACK is not received from sip:[email protected]

I have tried everything I can think of. My provider, who is not the problem, has tried earnestly to help. I am not yet an MSP with 3CX, so they won't talk to me. I am at my whits end and would appreciate any help or guidance.

 

[YiannisH_3CX]

Calls dropping at the 32 seconds mark usually mean only one thing. After the call is established the ACK message is not received which causes the call to drop after 32 seconds.
You will need to run a packet capture on a device and the PBX and see capture a call. Then check the captures and look for ACK messages. You should see one side sending 200 OK messages for 32 seconds without getting a reply and then dropping the call.
If that is the issue then you need to see which side is not sending the ACK message and look for the cause.