As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AIRCRAFT DID NOT ACCEPT APU ELECTRICAL POWER AFTER LANDING SHUT DOWN APU. SUBSEQUENT RESTART OF APU INDICATED LOW OIL PRESSURE AND FAULT LIGHT. NO RESTART ACCOMPLISHED. FAULT WAS VERIFIED A HARD FAULT NO APU ROTATION. REMOVED AND REPLACED APU STARTER / GENERATOR, OPS CHECK GOOD MM REF 49 41 21 400 801 AND 49 41 21 000 801 GROUND VERIFICATION CHECK GOOD IAW MM 49 41 21 400 801.