What was found
AC WILL NOT TAKE GROUND POWER. GROUNDED - YES. FLIGHT CREW FURTHER CLARIFIED THAT APU WOULD NOT START, NO GROUND SERVICE POWER (SYMPTOMS DESCRIBED IN B737-9 IFIM TASK 24-22-00-810-801). REMOVED AND REPLACED AUXILIARY POWER BREAKER C803 PER B737-9 AMM 24-21-41. ALSO REMOVED AND RE-INSTALLED #1 GCB C801 FOR ACCESS. ALL INSTALLATION TESTS PASS. GROUND POWER, APU, AND APU GENERATOR ALL OPERATE NORMALLY. ETOPS GROUND VERIFICATION SUCCESSFUL.