Grump: “You did flip the lever to engage the drive, right?”
I think Grump got this one. The description should have been something like, “When I flip the lever back and forth the clutch jaw does not move”.
http://apache.ariens.com/manuals/PRM-10000.pdf
On page 12, the lever (32) should move out the clutch fork (39) which will push the clutch jaw (42) on the bucket into the clutch coupling (page 11, 116) on the tractor drive.
If that isn’t happening then the parts might be frozen but then you would not be able to flip the lever. If you flipped the lever and the jaw did not get pushed out then one of the two roll pins (34,40) or cotter pin (38) is probably broken.