gear problem on my citroen dispatch 2L hdi?

hi...my citroen dispatch 2001 2L hdi wont go in gear with gear stick...if i use the gear arm next to gear box it does go in gear....ive put it in neutral moved gear stick up..down..side to side...all gear rods move as they should...could it have disconnected from inside gear box ?...cable looks ok ....if i move gear arm next to gear box the gear stick moves up and down as if not broken...i would be gratful for any help on how to fix thx