Randomly, Incoming calls from SIP trunk are getting "CONGESTION" and 3CX is reporting ACK not received

[ezamora]

Hi,

We are randomly (70% of all incoming calls) receiving a busy tone calling to any SIP trunk configured at that particular 3CX installation.

Our SIP provider (Vitelity) is reporting a "CONGESTION" message from 3CX and 3CX is showing: 03/01/2021 3:07:05 PM - [CM503021]: Call(C:33): ACK is not received from sip:[email protected] (Vitelity) at its activity log.

This PBX is running perfectly since 2017. Nobody has changed anything (Firewall/AV/router conf, etc). The Firewall test runs all green.

Could you please assist me?

Zeke

 

[YiannisH_3CX]

Hi Zeke,

Could it be that you hit the limit of the SIP Trunks channels or the PBXs simultaneous calls?

The error the PBX shows should cause the calls to drop after 32 seconds and not give a busy signal to incoming calls so i do not think its relates although you should have a look at it and see what is causing this.

Give us some details of your system like described here: https://www.3cx.com/community/threads/information-to-provide-when-requesting-help.67558/

Also let us know if you have multiple DIDs / Inbound rules and if the issue occurs when calls are going to a certain destination.