Sounds like the pre-load tension on the awning roller on that side has slipped. If you have the manual for your topper, the procedure for tightening the topper should be in there. If you don't have the paperwork, someone here might, if you have the make and model of the topper.
Otherwise the web (or your dealer) is your next stop.
Lou and Laura with Bella - German Short Hair Pointer
2008 GMC Sierra 2500HD Crewcab SB Allison Duramax
2010 Flagstaff 8526RLWS - Superglide 3300
HAM CALLSIGN - KC3FFW