3CX and custom roms

[Siegfried_Kaos]

I have 3 phones I've tested 3CX on, and only the one without custom rom will accept incoming calls. I understand that is because of the push settings. I wanted to try a different app, but attempts to configure it got me blacklisted from even logging in to the management console. How to solve?

I last used 3CX about 10 or more years ago and don't remember it being this difficult to get working.

 

[Siegfried_Kaos]

I just tested everything again, and I'm not sure how but I have all phones accepting calls now on the 3CX app.

 

[OlegR_3CX]

Hi there. I've also tried and used custom ROM, in my case, Lineage OS 20 for Oneplus 5 and it works just fine for me.
I could only think of the SSL QR provisioning if some of the SSL will not be updated on the OS, but in your case, you mentioned the blacklisting IP, so it should be something else and perhaps related to the networking.