I have the same problem when turning on the push notification I loose my connection.
I am based in Canada.
iphone 8, IOS 13.5.1, Zoiper 3.30.1
I read on on on another thread (which I can't find anymore) that there is an issue for people located outside of the USA. Something to do with Apple. Is there a solution by now?
sometime it shows: Call leg/Transaction does not exist(481)
or Push server is unable to connect to Home Registrar. Please...