Cant tell if this addon is glitching or not?

im trying to get these to overlap with the textools addon but when i select one of them and press “similar” it says “please select only 1 UV island”…
also, when i try to align it just makes them disappear.

Are they from one object, or several objects? TexTools doesn’t have full support of multi-object editing yet. In fact, it had none until @franMarz added some today:

I bet these islands belong to different objects, as @Stan_Pancakes said. Crop, Fill, Align, Sort, Straight, Edge Peel, Iron Faces, Get Texel Size in Edit Mode, Apply Texel Density in Edit Mode, Combined Scale mode and Select Similar are lacking for multi-object support at the moment, and won’t be as easy to implement as it was for the operators I updated these days.

They’re not. They’re part of the same mesh.

…a very vague thought here, but could it be you have 2 UV maps on your mesh object by any chance?

Blender version? Are you using the latest release of TexTools?
Ultimately, can you share the file?