B777 Captain reported during pushback; the cockpit screens went blank then returned with numerous EICAS massages and an automatic engine shutdown. This resulted in a return to gate.

Narrative

Captain; First Officer (FO) identified Threats of Technical; Maintenance (Electronic Engine Control (EEC); Lower body Overheating) during preflight planning. Mitigation was to call Maintenance Control with Dispatch in the loop to discuss actual write ups. During call; Maintenance Control advised the EEC was a 'nuisance' warning; and the lower body situation was scheduled to be fixed in four legs; ZZZ1 turn; ZZZZ turn and back to ZZZ. Captain; FO were satisfied with explanations. In addition;during preflight duties Maintenance personnel visited cockpit numerous times working on the RT ENG STBY GEN bug oil levels. Eventually the flight took a delay of about 27 minutes to get ETOPS check and new maintenance release. Push back was normal to the green line. Once cleared to start; FO stared both L/R engines per Flight Manual (FM). Both engines started normally. Captain called for after start checklist; FO set flaps; both pilots did their respective flows; including flight control checks. FO stared calling off checklist items and all cockpit screens went blank with electrical relay switching noises. Next; the cockpit screens came back on line with numerous EICAS messages. Captain FO confirmed RT ENG N1 at 3% and no ENG FAIL warning EICAS or Master Caution. FO contacted Ramp to get a visual and see if there was any abnormality in RT ENG advising them of ENG FAIL. Auto relight did not function and a short while later the Auto Restart Check lists represented on the EICAS. Crew accomplished checklist. Crew contacted Hub Maintenance and they advised crew to contact Maintenance Control prior to pulling back into gate. Crew accomplished and Maintenance Control Engines did not have any idea why the RT engine rolled back and shutdown. Crew Coordinated with Ramp for crew to tug jet back to gate. Southeast taxi was not used due to difficulty in taxi on southeast with heavy aircraft and need for precision in parking. Crew advised Flight Attendant (FA); and PAX (Passengers) of situation and return to gate. Tug crew hooked up aircraft and moved aircraft back to Gate XX without incident. Only issue with tow in was tug crew did not utilize standard phraseology as listed in supplemental check list for tow in.was. Once at the gate; Captain coordinated with agents; advised PAX of situation; briefed Purser. Maintenance personnel met aircraft at gate; but waited 5 or more minutes before coming to cockpit. Captain called Dispatch (during shift change); stated he was not comfortable taking this aircraft on an ETOPS flight and requested another aircraft. CA then called Chief Pilot advising to assist with operations and finding a few aircraft as he was not comfortable taking this one. Chief Pilot assured Captain this was not an issue at the current time and advised Captain to make multiple write ups in logbook detailing what went wrong. PAX were unloaded and Captain debriefed FA crew as to what had happened. Captain called Dispatch again and was advised flight was cancelled due to inability to get new aircraft in time for flight and curfew at ZZZ1; this was via Operations Manager. Dispatch further stated the jet was going to get an engine change. Crew exited aircraft; Captain made announcement a the gate advising remaining passengers in boarding area of regret in not being able to fly to ZZZ1 due to aircraft availability and departure time to make the curfew time at ZZZ1.