The fabric can be "slid" either way, but take the tension off first. (Open all the way, then use the rafters to create a little sag in the fabric.) Then the pulling begins.- just grab whichever end and pull it into position.
Most awnings have retaining screws in the fabric to prevent such shifting- those have to be removed before adjusting, of course. Though yours might have fallen out already, letting the awning shift. Once you've got it corrected, be sure to replace missing screws.
" Not every mind that wanders is lost. " With apologies to J.R.R. Tolkien