Attempt to upload, or build and test anything.
The SDK, regardless of version (Unity or SDK), type of internet connection, logging in and back out again. All results in the SDK stating that "[Always] Attempted to load the data for an avatar we do not own, clearing blueprint ID".
My account is still in good standing, I've been in talks with support for 3 months now trying everything that I'm able to do on my end other than reinstalling my OS (Windows) and as of yet, it still doesn't recognize that I own my own Blueprint ID's.
The only other answer is that for some reason that seems to be entirely Unity/SDK independent as I've tried this on every possible combination of Unity and VRChat there is, with and without extra packages, all installed with VCC (and without), the authentication doesn't recognize any of my projects (completely new project, existing project, world or avatar etc.) when I attempt an upload of any kind, even stating during a Build & Test, that I'm attempting to load an online world in offline mode, despite opening from the SDK's Build & Test directly
Moreover it's inconsistent enough that every time I open Unity or one of my projects (again, new or old) It throws entirely different errors and warnings (see certain screenshots below).
One of the persistent bugs that accompanies this is the "Capture from scene" button not capturing an image and saying it has anyways (this behavior doesn't fully affect results as selecting an image manually still results in it believing I don't own my Blueprint ID).
Another one of said inconsistent bugs is ClientSim refusing to move past the first screen and breaking entirely (warning screenshots are all I have of the console mentioning this accompanying bug).
And the Assembly Updater Warnings seem to only pop up when I first load back into a project (I assume a PC restart gets them to show back up again).