If a disk volume in Windows platform is found to be dirty, the volume is marked offline. Any attempts to access the volume will result in error. Clean up the volume and manually bring it back online.
If a mount path directory is deleted or renamed (that is, through the operating system), it is not recreated the next time a data protection operation attempts to accesses the mount path. The mount path becomes inaccessible for the job and hence the mount path is marked as offline. Attempts to back up to that mount path will generate error messages.