Replacement back panel coming off

I replaced my back panel several weeks back with a kit purchased from ifixit. Followed all directions from the walk through and general steps from multiple other sites .

Within 24 hours the sides and edges are starting to come up and within a week the whole back panel wants to come off completely.

Each time I removed the adhesive and used the leftover from the supplied adhesive provided in the kit to re-apply.

Each time, same thing. I tried this 3 sperate times…

I even tried heating the phone and adhesive up before and during applying it. I also used clamps and left them for 12+ hours to insure a seal.

I feel the adhesive is bad but want your thoughts before I reach out to support.