What was found
R PACK OFF EICAS MESSAGE APPEARS DURING TAXI, UNABLE TO TROUBLESHOOT VIA QRH, MEL NOT CREW DEFERRABLE ETOPS 180, IN AUTO POSITION OR N POSITION PACK OFF STAYS ILLUMINATED AIRCRAFT BACK TO BLOCK AND GROUNDED BY MAINTENANCE. MAINTENANCE REMOVED AND REPLACED FLOW CONTROL CARD ASSEMBLY (M864 AT P50 PANEL) IAW B767 AMM 21-51-09, NO HELP. DEFERRED PER 21-51-3-1. PLACARDS INSTALLED. MBCB 10/30/2022. MEL MAINTENANCE PROCEDURE COMPLIED WITH . NO DEACTIVATION PROCEDUCE - LEFT PACK AUTO DEFERRED. AIRCRAFT RETURNED TO SERVICE