As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
AT FL 400 ATTEMPTED TO START APU 10 HRS INTO FLIGHT. APU WOULD NOT START. APU HANGS BETWEEN 30-50%, 3 ATTEMPTS ALL FAIL. APU MX MSG NR 49-10291 NOT ACTIVE. PERFORMED ASSOCIATED FIM TASK VISUALLY INSPECTION APU, NO LEAKS NOTED. SERVICED APU WITH 1QT OIL. APU STARTS & OPERATES NORMAL ON GND.