subaru engine conversion started twice now will no longer st

[Rusty Bus]

I have just put my 2.0 N/A in my split and it started twice and ran like a dream. tried to start about 5 mins later and it wont start. it has the symptom's of the timing being out. It backfires through the air filter and I got a couple of flames out the exhaust

I have tried the diagnostics and all I get is the check light constantly flashes on and off evenly

Has anyone had this problem or knows what this flashing means

Cheers

[Rusty Bus]

All sorted, runs like a dream

Fitted a new set of plugs last night, starts and runs fine now. The old plugs looked fine so surprised this prevented the engine from starting when it had already run