Z axis belt issue

The belt in my z axis locks together and doesn’t move at all


Any thought? It was working fine, I just disassembled to retram.

That is correct. It is the belt being unmovingly connected to the stationary pulley which allows the motor to push/pull the Z-axis down/up — if that pulley allowed the belt to spin, then the motor would simply spin the belt around and the Z-axis would not move.

Sort of like:

http://507movements.com/mm_013.html