Bob,
Titus was a big help. There's a good video here:
https://www.youtube.com/watch?v=kLlgHPgg1_8
You aren't trying to remove a shelf, you are trying to remove the floor
of the cabinet, yes? After you loosen the locking screws, tap the walls of
the cabinet gently with a hammer to widen the bottom so that the locking
pins clear the holes on the floor. I'm afraid this may be a major
disassembly project. Are there connectors along the back, also?
Seems to be an over-complicated gizmo to do a simple job. Good luck
Dave M.