AAAAND I fixed the problem myself. If anyone has this issue in the future, here was my issue: some unknown serial monitor was for some reason using that COM port (5 in my case) immediately. No idea why. To fix it, I went to Device Manager, found my Arduino under Port > COM5 then Right-Click > Properties > Advanced Settings. From here, I manually changed the COM Port from 5 to 100 (you can pick any number lol).
I don’t know how to figure out what was using my COM5 port as soon as it was plugged it.