As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
FLIGHT NUMBER 126, DURING CRUISE APU FAILED TO START DURING INFLIGHT START VERIFICATION (5 ATTEMPTS). MAINTENANCE TROUBLESHOT PER FIM 49-11-00 TO FAULTY EXCITER UNIT. REMOVED AND REPLACED IGNITION EXCITER IN ACCORDANCE WITH MM 49-41-03. APU OPERATIONAL CHECKS GOOD.