The following error may occur when using Voyager's Management pages:
Solution
Stop Voyager
Go to the [Install Dir]\data\config directory
Make a copy of the security.dex file as a backup and save it in a different location
Delete the existing security.dex
Restart Voyager (this creates a new security.dex file)
Login using internal authentication (default should be set to admin/admin)
Re-register the AD groups
Notes
If you have not saved your list of AD groups, you can use a tool such as PsGetSid to recover null group names from SIDs in the backup copy of the security.dex file
You may need to re-associate Saved Searches with Invalid Display Templates with valid Display Templates