The car won't fire it keeps back firing - i did have this running about a month ago but recently just give up

new cps 0.8mm, phase 0.25mm, new plugs, leads & tried replacement coil and nothing - it has a spark and a good one but won't fire.
The only thing is the fuel was 18 months old and i topped it up with a gallon of fresh is it likely the fuel is bad or should i be looking in another area?

Timing appear fine as the engine was just rebuilt and everything lines up as it should?