If the file was properly recovered, replaced, or deleted, you can remove the file from the list of disabled files (re-enable ...

If the file was properly recovered, replaced, or deleted, you can remove the file from the list of disabled files (re-enable the file) by clicking the  File tab, clicking Options, and then clicking Add-Ins. In the Manage list, click the arrow and select Disabled Items, click Go, and then select the disabled item that you want to re-enable.