Grandstream GXV3175v2

i have some problem to connect a grandtream GXV 3175v2 over openvpn to my freepbx server
Current Asterisk Version: 13.9.1
PBX Firmware: 10.13.66-13
openvpn is connect but the phone doesn’t register
can someone helps me
best regards

Please provide the configuration (in Asterisk terms, not FreePBX ones, of Asterisk, and of the phone). Please also supply the chan_sip or chan_pjsip debug trace for the failed register attempt.