Take the Plug out and check for spark in the plug,
If no spark then replace the plug and check again,
if spark is good then check compression in the cylinder with a pressure gauge,
if compression is o.k the could be a valve got blocked or something maybe covered in dirt and fuel is not getting to cylinder...

hope it's not you cylinder/piston/rings that will cause a compression issue mate.

if its a dirty valve sometimes a simple cleaner that you add to the fuel(like a BG44 etc'..) will help you clean the dirt off...

good luck.