Pull the handle and check the roll pin that acts as the pivot. Mine has done this several times and I finally picked up a spare handle.
The pin wears out and eventually slips down and out of the plastic, and then the "action" starts tilting just enough for the plastic gears to do nothing but slip when you pull the handle. The fix for mine? Force the handle (it's actually pretty easy) back to its own normal position, and drive the roll pin back up into the housing. Takes a few tries if you've never done it before.
Otherwise a replacement handle runs around $5 to $40 at a salvage yard. (our U Pull yard did mine for $3. The local truck scrap yard where the owner thinks everything is gold plated? Wants about $35 for the same thing)
S-