There is a chance that you don't have the right value resulting of the trimmer setting of the noise section..? I think that because of your snare missing the noise and clap doesn't sounding right. Also it's pretty unlikely to do another mistake with the noise circuit because it is small and it's likely to do the mistake of bad setting of the trimmer because it is needed to measure a little AC voltage, what is not possible with the ultra-cheap multimeters.

About cowbell and cymball not sounding at all, maybe try to see if there isn't any pins touching the body of their level potentiometer. Some are very close but don't have to touch otherwise the sound could disappear. That's what happened to me.
Anyway with the instruments which don't sound at all, this is very likely to be related with something about the amplifier.

Thanks I'll take a look , the noise section does work just doesn't seem present in the snare
I built very carefully triple checked everything , and all the parts added up at the end , but must have made mistakes somewhere , thanks for your tips

Cowbell and cymbal fixed just broken ribbon cable

Clap good now

Hi hats are still reall quiet

Snare sounds woody and tubby