Not synchronizing

I've already run through a lot of troubleshooting steps with a customer service agent, who unfortunately in the end was unable to help me.

Basically, my Lightroom CC on my primary user profile is stuck.

I can't open images to edit (they won't download fully from the cloud)

I can't upload new images, I can't delete old images, I can't organize files.

I've tried to "reset" my Lightroom by deleting the .mcat file and the entire .lrlibrary file, neither of which help. When I reopen Lightroom, it sits at "0 images" indefinitely, never downloading more images. According to the web-based Lightroom app, I have over 80,000 images.

When I open activity monitor, Lightroom is always running at a huge 90%+ of my CPU, and I can't just quit Lightroom normally -- I have to force quit from activity monitor. 

After going through support with an agent remote-controlling my laptop (nothing worked), we discovered that Lightroom works completely fine on a new "test" profile on my laptop with admin priveleges. It's a fine workaround, but I'd rather use Lightroom on my primary profile so I can export normally and use other software.

Lightroom CC is fully updated (version 8.5.1), I'm running macOS Tahoe 26.0.1 on a 2019 MacBook Pro. One day Lightroom worked fine, the next day it broke.

Any help is much appreciated!