How on earth do you import a mesh back in to SS

I'm so lost. I'm trying to edit a pair of wings I downloaded online to make them so that they fold together instead of extend out. I simply edited the original mesh but it doesn't import back into Sims Studio. It's basically the same mesh and but the geometry changed.

I tried to follow the steps from this tutorial but there are certain things that aren't happening. For example, it says the mesh will turn a different color when you select the right vertex group, but that never happens. So i have no clue which one is the right one

I used this tutorial to do the weights.

The mesh has 3 vertex groups:

Spine 0

Spine 1

and Head

I assume because the original mesh is supposed to be a stand in for a ring that is no longer there that that could be why I don't see it anymore.

However, I duplicated my progress and imported it into a blender file with the original mesh.

I did edit the mesh in the newest version because that is the version I am familiar with in terms of modeling and then imported a Collada file back into the older version. Im not used to the key binds in the old version and felt faster to do it in the new version

When that didn't work, I tried to just do everything in the newer version which still didn't work.

I am using the original UV maps the wings came with because I simply wanted those wings to be closed and I don't know how probable it is that the UVs are causing the problem but what do I know lmao

I deleted rig 001 because I heard that was something you had to do to get it to work too but no dice

Either way, I'm stuck and confused because nothing I seem to do imports the file into Sims Studio. This is the side of Blender I'm not normally using so I'm lost. Pleeeease help