Two log messages in your post:
first
00:00:21.250 [CM302001]: Authorization system can not identify source of: SipReq: INVITE 14@mydynamicdns.XXX tid=-2e1c7245 cseq=INVITE contact=16@66.166.166.55:51242 / 101 from(wire)
and second
00:00:21.250 [CM500002]: Unidentified incoming call. Review INVITE and adjust source identification:
provide hints for you.
Thanks Stepan. I have been trying to understand at which side to make changes, but have not succeeded. My best guess is I have to make a change somewhere in the 3cx setup. Any suggestions?

