Rufus is likely causing issues. By checking the box to skip the Microsoft account in Rufus, the local account is created and Windows can't look up the digital licence linked to your MS account in the previous installation. Try logging into windows using the same Microsoft account (Settings > Accounts > Your info > Sign in with a Microsoft account instead), leave for a few minutes then return to activation and click Troubleshoot. If it still doesn't work, you should see a link that says “I changed hardware on this device recently”. Select your PC from the list. This should work.
The phone portal won't work because the installation ID is created from the dummy key Windows created. This only works once you have installed the real key.
If you have the email or receipt from when you bought pro, the real key should be in there. Just enter this in using activation > Change product key and it should work.