Modern antivirus software (McAfee, Norton, Bitdefender, and even Windows Defender) sometimes misidentifies Proteus’s license validation mechanism as a "crack" or "keygen" and quarantines critical license DLLs.

If you are using a legal version provided by your university or employer, reaching out to your to refresh the network seat is often the quickest final resort.

By following the guidance provided in this paper, users should be able to resolve the error and continue using ISIS Professional without interruption.