As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
APU FAILED TO START IN FLIGHT PER THE FM LIMITATIONS. A BITE CHECK OF THE ECU WAS PERFORMED PER THE APPLICABLE FIM AND DID NOT REVEAL ANY FAULTS. A APU VERIFICATION FLIGHT WAS ACCOMPLISHED ON THE NEXT FLIGHT AND THE APU STARTED IN FLIGHT PER THE FM LIMITATIONS.