As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
WE CAN PLACE CALLS ON SATCOM AND HEAR OTHERS SPEAK BUT NO ONE CAN HEAR US. TRIED CALLING FROM BOTH MCDU'S AND BOTH PILOT STATIONS AND BOTH SAME EFFECT. GROUNDED-YES. COULD NOT DUPLICATE, ACCOMP VOICE TEST, REF B737-900 AMM 23-15-00. SYSTEM OPERATIONS CHECKS NORMAL.