I am using Zoiper and usually works great, with one huge exception.
If I tuen on my phone in the morning and I am outside the office, Zoiper will work fine outside the office all day long. On the other hand if I am inside the office on the office LAN WiFi I will connect and Zoiper will work fine all day long inside the office.
Now here is where the problem comes in, if I go from outside to inside or inside to outside Zoiper will not connect to my FreePBX / Asterisk PBX. Does anyone else have this issue? Is there a work around?