What was found
DURING ENGINE START, LT ENG NO ROTATION DURING X-BLEED START - RT ENG BLEED NEVER OPENED - TRIED MULTIPLE BLEED ISOLATION VALVE COMBINATIONS WITH NO ROTATION. CREW RETURNED TO THE GATE (BTB). MTC INSPECTED LEFT ENGINE ISOLATION VALVE AND CYCLED. STARTED LEFT ENGINE, RAN, ALL PARAMETERS NORMAL. LEFT ISOLATION VALVE CHECKED OK. REF AMM 36-11-04 AMM 71-00-00. AIRCRAFT REMAINS ETOPS 180 OPERATIONAL. A/C RETURNED TO SERVICE.