Unable to Unpark Call from Shared Park

[Jacob Grigg]

Hi,
Our phones are unable to unpark a call from a shared park via BLF. It was working fine for ~9 months then it stopped without making any config changes/3CX Updates/IP Phone Updates.

The setup is as follows:
3CX 16.0.8.9 hosted on AWS Lightsail
Yealink T42S, T46S and W60B phones
Phones use Direct SIP STUN
Cisco C1117 Router

Symptoms:
Parking calls works fine
BLF on T42S/T46S change to red when a call is parked and back to green when ended/unparked
When pressing a red BLF to unpark call the IP phone shows "Calling SP0", "Talking SP0" then phone returns to the "Home" screen and BLF SP0 stays red. The caller remains on hold but hears a slight click when the BLF is pressed.
Calls can be unparked and returned to the IP phone via the webclient.
The issue occurs with internal and external calls
The issue occurs with SP0 and SP1
When trying to unpark a call via BLF the following error appears in the activity log: Call to T:Extn:7331@[Dev:sip:[email protected]:5186] from L:20.1[Line:10001<<614xxxxxxxx] failed, cause: Cause: 481 Call Leg/Transaction Does Not Exist/INVITE from 103.xxx.xxx.xxx:5186

Things I have tried to resolve the issue:
Install 3CX updates
Install phone firmware updates
Reboot server
Reboot phones
Run Firewall Check - It passed
Confirm that the phone's Local SIP and RTP Port ranges do not overlap

Thanks,
Jacob

 

[cobaltit]

You mentioned running the firewall checker but not that it passed. And you haven't tried the one thing that will work and that's a SBC.

 

[Jacob Grigg]

@cobaltit
Sorry I didn't mention it before but the firewall checker did pass.
The IP phones connecting with direct SIP STUN worked fine for ~9 months before it had issues. I don't believe any changes were made to the 3CX Config / 3CX Version / IP Phone Firmware before it started having issues.

We were trying to avoid using an SBC for two reasons. The first being that all our server infrastructure is cloud based and we don't have any local enterprise grade servers. And the second is that we can easily send a phone home with a user if we need to.

I'll run a test using a Raspberry Pi as an SBC and see if it make a difference.