heres a link to the us .org site,
about 3 quarters of the way down the page is a post by trbig with a
cpl of pics of the gear shifter cover removed (i couldnt find another pic)
if u lean the bike up against the wall u can remove the cover and inspect
that the pins are still in there location and the shift pawl lines up,
other than that as melb stated could be a bent shift fork.