Recent Spay Issues

Recent spay problems

My 1st rescue was spayed 3 weeks ago. 1 week after bringing her home her stitches were not there (except the deep internal ones); there was a gaping hole at the site. There was no sign of infection to inhibit the healing of the skin. For another week I took her to the vet every morning, where he would just put on an antibacterial spray and bandage her up, and to monitor if the site was closing. It did not. So he put her under anesthetic for a 2nd time and put in new sutures. It is now 1 week later and they're out again! She still has a hole there and it doesn't appear to be healing much either. Still no infection either. I just cannot figure it out!

In Canada, when I would adopt a dog they always came already sterilized, so I have never dealt with a fresh spay before.

I am this close to just duct taping the site and checking on it in a month. Any ideas or information, anyone?