Error when trying to connect to GPOAdmin: "Unknown Error (0x80005000)" (4335758)

When connecting to GPOAdmin the following error is displayed:

System.DirectoryServices.ActiveDirectory.ActiveDirectoryOperationException: Unknown error (0x80005000) ---> System.Runtime.InteropServices.COMException: Unknown error (0x80005000)
at System.DirectoryServices.DirectoryEntry.Bind(Boolean throwIfFail)
at System.DirectoryServices.DirectoryEntry.Bind()
at System.DirectoryServices.DirectoryEntry.get_AdsObject()
at System.DirectoryServices.PropertyValueCollection.PopulateList()
at System.DirectoryServices.PropertyValueCollection..ctor(DirectoryEntry entry, String propertyName)
at System.DirectoryServices.PropertyCollection.get_Item(String propertyName)
at System.DirectoryServices.ActiveDirectory.PropertyManager.GetPropertyValue(DirectoryContext context, DirectoryEntry directoryEntry, String propertyName)
--- End of inner exception stack trace ---

This is most likely due to communication issues between the GPOAdmin server and the Domains or the DCs. Ensure that all the Domains that GPOAdmin has GPOs for can be queried from the GPOAdmin server. Check the GPOAdmin Event Log (found in the Windows Event Log under Applications and Services) for specific errors.

Ensure there are not servers in the AD Sites and Services that are no longer DCs, or are DCs that are not reachable. Check DNS to ensure there are no name resolution issues.