So a couple nights ago I was finishing up a session and saved and closed like I usually do, but when I went back my projects wouldn't load (I could only make new projects). 

I have since reinstalled Sonar, my audio drivers, and the software it gets stuck on scanning now (Softube Tape). I still can't open my old projects, only create new ones, and I didn't install/uninstall anything during the time it stopped working.

I've also ran windows update in the off chance it caused the issue.

Windows 10, Sonar Platinum (from Steam), Presonus Studio 192 Mobile.

Any input or things to try would be appreciated. I can't do anything right now :(

Open in SOANR's safe mode to find out if a plug-in is causing the issue. Also check whether there's a splash screen for Softube Tape hidden behind something (check the task bar), and if it uses iLok, check for the latest iLok drivers.

Hi. As Craig suggests, I would check for a hidden splash screen / window behind SONAR.
It does use iLok (I believe), so check for the latest release that were dropped a month or so ago.
IIRC, the older version could cause your kind of issue.
All the best.