Outer Limits 4x4 Board

hey guys i have a rear air locker fitted to my hilux, i went 4wding this arvo and was using my locker on and off but on my way home realised that it had'nt disengaged, so i flicked the switch in out a few times but still wouldnt come out. So i pulled the air line off the diff, to see if there was still air pressure in the diff, because i thought there may of been a block in the line some where holding pressure in there, but there wasnt. So i'm thinking there is something wrong internally. any help about this would be really appreciated.
thanx

try driving in reverse to get it to unlock, i have to do this but only in the front tho

thanx for ur reply try it in reverse still no luck

have you tryed jacking up the back end with both wheels off the ground and testing it ?