Everything works but my speedometer stays at zero

it means that either the cable that goes from gearbox to the instrument panel is not working, or the gear that rotates the cable in gearbox OR inside the instrument panel is broken, first check the cable and make sure it's not broken inside ( the inner cable) if it's broken change it other wise have a look inside the instrument panel (easier one first) if the small gear (it should be plastic) is not worn or anything then try having a look at the gearbox.
Hope it helps and please don't forget to rate the answer it helps me, thanks! it means that either the cable that goes from gearbox to the instrument panel is not working, or the gear that rotates the cable in gearbox OR inside the instrument panel is broken, first check the cable and make sure it's not broken inside ( the inner cable) if it's broken change it other wise have a look inside the instrument panel (easier one first) if the small gear (it should be plastic) is not worn or anything then try having a look at the gearbox. Hope it helps and please don't forget to rate the answer it helps me, thanks!