I guess it would be the obvious fault finding. Check the plugs for a spark, swap plugs over or replace, Ensure the battery is fully charged, ideally with a smart charger or test with a meter. I assume none of the connectors have been disconnected. I'm not familiar with MC11s, but does the ATAC valve have a servo?

Have you read this link as well http://www.nsr-world.com/workshop/wiring/electrex-fault-finder/Electrex_fault_finding.pdf
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