Oil pump drive gear stuck

Sometimes/ often, the engine has to be rotated to get the hex to engage the pump, before the drive will drop in.
But I agree with Plymouth65. That bushing if new, is supposed to be reamed to fit the drive, after being installed. If this is not done, then the drive also may not engage the cam, And with the bushing now tight on the shank, You can no longer turn it.

So now you could have a total of up to three problems.
IMO, you will gave to get it out of there somehow and verify both the shank and bushing diameters.
I have been down that road and for me it was not fun. Sometimes you can walk the out by upward pressure of a hook tool, while simultaneously twisting it back and forth with a very large one-piece-screwdriver. Resist the urge to use a multiple piece set-up on a T-bar, cuz if the tip falls off............. You will be even unhappier