As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
ETOPS SIGNIFICANT SYS - LOST ABILITY TO TRANSMIT MESSAGES TO ATC CPDLO. MESSAGE RECEPTION OK. NO FAULTS NOTED WITH SATCOM. RECEIVED OTHER ACARS MESSAGES WITH NO DIFFICULTY. RESET ACARS MU. CLEARED BUFFER. SATLINK TEST PASSED ON GROUND.