Is awning material held in place on roller with screws at each end?
Typically the material is held in place on rail (on side wall) with screws but not on roller.
Just hold awning arm with one hand and push roller/pull material with other hand to 'square' it up on roller.
Material should be same distance from end of roller on each end.
Mine would shift when fluttering from wind and I would have to shift the material to square it up.
After a few times I installed 1/4" short screws in roller grove right at edge of material. No more having to square up.