Shifting problem

[SSChevelle]

I am new to this site and trying to pick brains for the problem I have with my car. 1970 LS6, M22, new Hurst comp plus (set up on bench on tranny ) Shifts perfect while driving. When coming to a stoplight, put in neutral and let clutch out , shifter will not move when you try to put it in gear?? Has all new clutch linkage, clutch, everything is new. took to tranny shop they cannot figure out why this happens.

Any ideas out there?

thanks, Les, ( I have been driving BB Chevelles since 1967)