Some details here.
iOS Version: 11.3.1 (iPhone 6)
Using Zoiper for phone calls over the VOIP.ms service. Paid for Push Notifications (proxy protocols on SIP, and Push Transport on TCP). Force Background and Wi-Fi Keep Alive are both enabled.
My issue is that if I turn Zoiper on for the first time, it usually says "Not Ready" in red, then rapidly turns green and says 'ready' as it successfully registers. If I try to use it then, perfect.
But it seems to keep de-registering. I tried to give a call onto Zoiper after 2 hours to ensure it still worked - but Zoiper never ran. I turned it on in my iPhone - and it first said "not ready" in red first before successfully re-registering.
Is there any solution to this? I bought Push Notifications because I thought this would help - but it hasn't. I made sure that the account registered with Zoiper was using TCP for Transport (under Accounts, Network Settings) - that didn't seem to work.
Is there any trick whatsoever to making sure that Zoiper stays registered? I'm at a loss as to what the point of the service is if I can't be SURE that I will get my incoming calls.