I am using Zoiper for more than ½ year. Before no big problems.
Now I cannot make outgoing phone calls; at the beginning there was the "AUDIO error").
I checked the settings on my iPhone 5; the settings are all as required (e.g. "allow Zoiper to use the microphone, STUN is enabled, WIFI settings as described").
After I checked all the settings, unregistered and registered again, the AUDIO error-indication is gone; now the dialpad returns after about 20-30 seconds to the call history.
No problems in receiving calls.
Can anybody help me ?