Use proper nouns whenever possible.
We're talking about classic EVRSI activation, here, so we will restrict the discussion to that old-fashioned, floppy-disk based system.
It sounds to me like the EVRSI.SYS file on your hard drive was corrupted. This can happen from antivirus software action, drive compression software, or careless use of EVMOVE or EVRESET.
This means that the activation license that was on your hard drive is gone. Dust in the wind.
The standard mechanism to recover from this is to Reset the activation on the floppy disk, delete the EVRSI.SYS file on the hard drive, and move the newly reset activation back to the hard drive.
To do this you will require the original activation floppy and will have to make a phone call to Rockwell Automation Technical Support (440) 646-3434 to get a Reset code.