I have this add on that I'm updating... preferences aren't saved after blender restart

here’s my add on that I’m trying to update:
https://drive.google.com/file/d/1NJjHROeh--LRIDInNm7piS9RFYTO1UDr/view?usp=sharing

the relevant code is in the SSM _preferences file I’ve double checked it with a smaller working add-on where the preferences do save and everything lines up as far as I think the code is identical between them or the usage of the code.

The bpy.types.AddonPreferences class is inside the SSM _preferences file…
and is set to “package” because it is a multi file add-on…from what I read online that’s correct

bl_idname = package

i’m registering an unregistering all my classes in a loop in my init.py so not sure if that is the issue

Any help on this is appreciated!