car will not shift?

i have a 1998 Honda accord ex coupe 4 cylinder f22b1 that has been converted to a manual and we did not know until a few months after i bought the car and there's been problems with it time after time but this time my car will not shift and mechanic recently fixed it i can put it into all gears and it wont go anywhere but the car starts just fine the mechanic also said the clutch was fine so i don't know why else the car will not move while in gear i am also 19 and i do not have much money so i am looking if there's a easy way to work on this i worked on Toyota mostly so i do not know much about Honda that is why i am asking.

and another reason i am asking is so i can sell it and buy a better car u cant get money out of a non moving vehicle but if i can get it moving again i can get a little more out of it