Depending on age and model of topper, Carefree used the lever and plunger on only a few models. Others use a spring and a ratcheting mechanism internally.
As a temporary fix to get home, maybe a large tie strap on each end of the tube to the side brackets, or a bungee rope over the entire awning end to end to immobilize it. You should be able to feel if there is tension on the tube when trying to take the slack out of the fabric.
'16 Outdoors Timber Ridge 280RKS
Reese 1700# Trunnion w/ DualCam HP
'03 EXCURSION XLT V10 4.30 Axles