Normally a simple fabric adjustment along the roller tube will get the awning arms to seat properly when fully retracted.
Here's what I do (electric or manual): This process shouldn't require any fabric adjustments along the fabric rail-trac that's attached to the sidewall of the RV.
Extent the awning fully and place the awning roller tube in it's lowest position (adjust at the arm joint). Using a step ladder (careful here) or stand on picnic table confirm that there aren't any screws placed through the fabric edge-ends into the roller tube (normally there aren't), if there are remove them. You want the fabric to be able move freely within the roller tube slot.
At one end of the roller tube (coin toss which end) grab the fabric flap with one hand and the main fabric with the other, then "tug" the fabric toward you 1/2" -1" along the tube with your body keeping the roller tube from moving during the tugging process. The fabric initially may require an extra "tug" to get it to start sliding within the roller tube slot. If using a ladder have someone hold the ladder.
Stepping down from the ladder re-adjust the awning arms (electric awnings) so the awning tube is in the proper position for closure, then retract the awning to check for arm alignment results. This initial check will confirm which direction (right/left) the awning fabric needs to be "tugged" to correctly align the awning arms. This process may take a couple fabric "tug" visits to one, or both ends of the roller tube.
Once you found the proper fabric location along the roller tube allowing for proper arm alignment for complete awning closure, take a magic marker and place a witness mark on each end of the roller tube next to the fabric edge....., should the arm alignment need attention in the future the magic marker reference will expedite the alignment process.
I've used this process on a number of awnings (mine included) and seems to get the job done.
2016 GM 2500HD 6.0L/4.10
2018 Jay Flight 24RBS
2002 GM 2500HD 6.0L/4:10 (retired)
2005 Jayco Eagle 278FBS (retired)
1999 Jayco Eagle 246FB (retired)
Reese HP Dual Cam (Strait-Line)