Do you hear a ticking noise as you raise the roof? There is a pawl system that prevents the winch spool from unwinding, and you will hear the distinctive ratcheting as you raise the roof.
Yours looks different from how I recall mine did, but I am pretty sure it relates to the spring and pawl you see near the wall above the spool, but it looks like it is on the wrong side to engage with the gears?
Ads @Colorado says, an internet search will probably find a video or instruction manual.
ETA: popupparts.com has a variety of winches available for $200ish depending on model. They should be able to confirm fitment; they ask for year, model and VIN number to confirm.
2011 Jayco X19H (purchased 2015)
2008 Jayco 1007 PUP (purchased new, traded for the X19)
2018 Nissan Titan Midnight Ed.