Make sure the Root Directory locations for all Endpoints are correct under the Accounts section of the RBS Manager, and that each Endpoint's backups are in fact under that path. 

Also, check the Root Folder path under Tools -> Properties of the RBS Manager, and make sure that path exists. 

Make changes if they are not pointing the correct locations, and Restart your server. Run the Server Tester to make sure it passes. 

Make sure the path for the rbs.mdb file is correct. Although it may show the correct path, remove the path and add it again. 

1. Go to Control Panel -> Administrative Tools. 

2. Select ODBC Settings/Data sources. 

3. Click on the "System DSN" tab and you should see the "RBSDB" data source under "Name."

4. Double-click it and another window pops up. That’s the ODBC Microsoft Access Setup window, with Data source name, description, Database, etc..

5. Click on the "Select" option. This pops up another window which says "Select Database." 

6. Make sure the path for the file "rbs.mdb" is correct. Although it may show the correct path, remove the path and add it again.

7. If its path is not set correctly (doesn't point to the folder where your actual rbs.mdb file is), correct the filepath.

 
Restart your server. 

If it still does not fix the issue, Uninstall the RBS Server and Reinstall.