As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
UNABLE TO CONNECT TO MEDLINK VIA SAT 1 OR SAT 2 FMC SHOWED CONNECTED, SAT 1/2 BLUE LIGHTS ON AFT PANEL WERE ILLUMINATED, BUT NO SIDETONE IN PILOTS HEADSETS COULD BE HEARD AND NO COMMUNICATION COULD BE ESTABLISHED. GROUNDED - YES. CONFIG A/C FOR MEDLINK CALL WITH SATCOM 1 AND 2, DISPATCH VERIFIED CALL, SATCOM TEST NORMAL REF B737-900 AMM 23-15-00-730-801.