A learning experience
When I were a lad, long ago, I was a mechanic for a while. I remember I completely rebuilt a small engine on a plate compactor. And it wouldn't start. Not a bit of it. Spark - OK. Carburetor - OK. Compression - OK. But didn't even TRY to start.
After 2 days of intermittently working on it, I finally took out the NEW spark plug and put the old one back in. Engine started on the first pull. (See Icon.) But it was a valuable learning experience.