When you create a plansheet, it's tied to a particular database.  The plansheet needs the TVD database to pick up its audience information.

 

 

But what happens if that .tvd database file is moved?  Or deleted? Or if it winds up on a different computer or server that can't be reached?

 

The plansheet is no longer able to reach the audience data it needs, and TView shows this message:

 

 

 

You can then navigate to wherever that database file is now living, and the plansheet will be happy again.

 

If a database is completely gone, such as if it's been deleted, you'll need to re-create it by building the script again.  And what if the script is missing as well?  You can recover a script from the plansheet; read I Can't Find My Script File.