Why can't I install RealFlight 9 online updates?

Some RealFlight 9 owners have been unable to download and install online updates successfully due to virus protection that's active during the attempted update. If these symptoms describe your situation, try the solution that follows:

• You receive error message "KEError 21091: The requested functionality is not available" when you try to update RealFlight.
• One or both of the following files is missing from your computer:
  • C:\Program Files (x96)\Common Files\KnifeEdge\CopyLaunch9.exe
  • C:\Program Files (x96)\Common Files\KnifeEdge\LauncherHelper9.exe
• You have antivirus software such as McAfee, Bitdefender, or Trend Micro running on your computer and providing some type of real-time/heuristic protection.

You may not be aware that antivirus software is active on your computer, or will have to look hard to find it. But if one or both of the files mentioned above is missing, it's almost certainly due to antivirus software intervention.

SOLUTION: Remove the file(s) listed above as missing from quarantine. Then, try the online update again.

To prevent future occurrences (depending on your level of comfort and technical knowledge), you can either: (1) disable all antivirus software during online updates, or (2) add exceptions for the files/directories above as appropriate.

Unfortunately, we can't provide exact instructions for your specific antivirus software. You may need to refer to its documentation for further assistance.