Summary
Error
Fix
Another way to do the same thing (unregister the plugin) is to use MOB like this:
1- Open your favorite web browser and go to https://<vcenter_server_name>/mob
2- Click “content”.
3- Click “ExtensionManager”.
4- If “com.HewlettPackard.DataProtector.VMwareGREAng.WebClient” is listed then
Data Protector Advanced GRE plugin is still registered. To unregister it:
a- Click "UnregisterExtension".
b- A new window will open. Paste the “com.HewlettPackard.DataProtector.VMwareGREAng.WebClient” string in the "Value" field and click Invoke method.
c- Close the Unregister Extension window and return to the Extension Manager.
d- Refresh the page and verify that the extension is now deleted.