Have I broken my Laserjet 2100?

[SimonMatthews]

I bought a maintenance kit for my Laserjet  2100. After replacing the separator pad, it would not pick up paper, so I thought that perhaps the extra friction on the separator pad was too much for the pickup roller, so I proceeded to install the new pickup folder.

Having replaced the pickup roller, it still did not feed. In fact, I think that it fed even less (before replacement it moved the paper a little). Disassembling it a little more to look at the shaft that drives the pickup roller, it appears that this shaft is not turning. On my second try to replace the pickup roller (I think that it was actually properly installed first time, but, since it wasn't working, I decided to rotate it 180 degrees on the shaft, so that the flatter side of the roller was facing away),  I got a nasty clicking sound on turning on the printer and when attempting to get it to print.

Have I broken whatever drives the shaft that drives the pickup roller?

[Repairatrooper]

If you have the roller inserted wrong, it can cause too much friction. These machines can sometimes be tricky to get the roller seated properly. Flat side should face down. I have also seen cases where either the end of the drive shaft gets broken or the shaft gets dislodged and major disassembly would be required. You should not be able to manually rotate the roller easily and if you can that would be a sign that something is not seated properly.

[SimonMatthews]

I am quite certain that the roller is engaged in the end of the shaft. I can't turn the roller manually.

When I try to print, the roller doesn't turn, but the printer emits a series clicking sounds, perhaps like a plastic gear is slipping.