Due to macOS limitations, VirusBarrier does not have the proper permissions to move or modify certain files. This is true with files located in a Time Machine backup as well as some other specific type of files. If you are unable to Quarantine or Repair infected files that are found, this is due to this particular limitation.
If VirusBarrier identifies any files that you are unable to Quarantine or Repair, you will need to Trust the files and remove them manually.
You can search for these files using the Finder or Mac OS X's built-in Spotlight search feature. If the files are located on a Time Machine backup, you can find instructions for deleting the files here:
Remove an Item From Your Backup Disk