Good Day,
These are the ports I have forwarded to get the Connect app to work:
3500-3501TCP, 5060-5061UDP and 10000-20000UDP
However I have experienced the same issue with the buzzing using the Mobile App that you are currently having. The QR codes that are generated are for the Connect App once it is installed in the Addons section. I am not sure if the Mobile App QR codes stop being generated once Connect is installed. Based on the configuration steps that were outlined below, it is possible:
https://forums.vitalpbx.org/t/how-to-correctly-configure-vitalpbx-mobile/899
Edit: I just checked it, it seems Connect replaces the Mobile App in VitalPBX version 4. On the Google Play store, the app states in the About Section:
About this app
VitalPBX Mobile is a powerful softphone designed for your VitalPBX phone system. Easily register your extension using our QR code, make audio and video calls to other extensions in the office, and communicate with co-workers using our chat feature.
Important: This app only works with VitalPBX v3.
If you want to learn more go to https://www.vitalpbx.org
I think this answers your question if you are using V4 and not V3.