Hello,
Can you please check which codecs are required by your PBX? In Zoiper H263+ and VP8 are available for everyone.
Can you tell us what is the exact issue that you are facing, e.g. is there no video stream, iare you unable to find the option to upgradety he call to video, etc?
Another thing is to try TCP as transport if you have too much codecs enabled, or disable some codecs if using UDP.