When the program detects a mismatch—even if caused by a corrupted update rather than a crack—it throws the Sign Check Error as a safety mechanism. It is designed to prevent malware from hijacking the drivers (which run at the kernel level).

This is the most common fix when the system refuses to load the virtual drive driver. Restart your PC while holding the key.

Temporarily disable your antivirus software or add Daemon Tools Ultra to the antivirus software's exclusion list. Some antivirus programs may interfere with Daemon Tools Ultra, causing the Sign Check Error.