Re-installing
Try uninstalling and reinstalling again.
Uninstall Opera GX (don't choose to delete your data when asked).
After Opera is uninstalled, delete its install folder. It should be the "Opera GX" folder in "C:\Users\yourusername\AppData\Local\Programs" by default, but it might be in "C:\Program Files" or "C:\Program Files (x86)" depending on how Opera GX was installed before. Anyway, just make sure the "Opera GX" folder is gone.
Then, delete everything "C:\Windows\temp" and "C:\Users\yourusername\AppData\Local\temp" to clear your temp folder (don't worry about the few files you can't delete because they're in use).
Then, download the Opera GX installer, launch it, make sure "Install for" is set to "Current User", make sure "Install path" is set to "C:\Users\yourusername\AppData\Local\Programs\Opera GX", adjust all the other options as you like and install.
See how that works.
If Opera GX still doesn't load, rename the "Opera GX Stable" folders in both "C:\Users\yourusername\AppData\Roaming\Opera Software" and "C:\Users\yourusername\AppData\Local\Opera Software" to "Opera GX Stable old" to test Opera with fresh data and settings.
If that works, the issue is in your "Opera GX Stable" folder (likely the Roaming one) somewhere.
Note that in Windows Explorer (File Explorer), you'll want to click "View" on the toolbar, goto "Show" and enable "file extensions" and "hidden items" so you can see and browse the app folder and see extensions for files.
If Opera GX still doesn't work, I would temporarily download and install Chrome, Vivaldi, Brave and Firefox to test if they have issues too. That might tell you if it really is a Micrsoft Family issue or not.