As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CPDLC WILL NOT ACCEPT CONFIRMATION MESSAGE RESULTING IN "OPEN" ATC MESSAGE. WORKED ON THE GROUND WHEN ACCEPTING PRE DEPARTURE CLEARANCE. AFTER ATTEMPTING TO RE-LOGIN, IT TOOK APPROXIMATELY 10 MINS FOR ATC TO ACCEPT LOGIN. GROUNDED - YES. RESET CPDLC SYS PER B737-9 AMM 34-61-00-800-899 PERFORMED FUNCTIOAL TEST OF CPDLC SYS PER B737-9 AMM 34-61-00-720-899 TEST OK.