Final Cut Pro Quit Unexpectedly - Can't Find Fix

My system was working perfectly, then I decided to buy an M.2 NVME drive and reinstall the system onto that instead of the SSD I had originally.

So, I got everything up and running again, and everything seemed to be perfect. Sound worked. USB worked. Wifi worked etc.

Then I went to reinstall FCPX from the Apple Store. Opened it after the install, and it comes up saying it has crashed unexpectedly, and doesn't open.

Has anyone else experienced this? or know what might be wrong?

Note: FCPX worked fine before, when on the previous SSD.