Hard to tell from just a picture but it looks like a lot of wear has occurred across that area and especially where the strap connects to the bag. Have you been walking with it reversed like a lefty? That might have contributed to the issue. If you still have the receipt you can take it to your retailer and see if they will attempt to claim a warranty on it, although unlikely as they only cover defects for one year, not excessive wear for an older bag. Good news is there are some really nice new models available or you might seek out a luggage repair shop to fix this zipper.

Let's hope you can get it sorted but it does look old

I assume it was purchased new

that looks like it went through hell and back. good luck with it.

I would probably just buy a new one.