I also tried to register Linphone (Android and PC) to a pjsip extension with similar problems, however my pjsip channel was ruining on a non standard port (5062) and I suspected that might be the problem.
Unfortunately I couldn't change it to 5060 to test as I have chan_sip running on 5060 which is the main channel I am using on my PBX and so far my attempts to try and move to pjsip have been pretty disastrous.