1. Click on the File tab in the top-left corner of the main Outlook window.

   

2. Click Options.

   

3. Click Add-ins in the left column of the next window.

   

4. The list of add-ins is separated into three sections - Active, Inactive, and Disabled.

   Note: The exact steps you need to take are different, based on the section in which the add-in is listed.

   • If the add-in is not listed in any of the three sections, reinstall the add-in and restart Outlook. If you still do not see it, go back to the beginning of this guide.
   • If the add-in is listed in the Inactive section, go to enable the inactive add-in.
   • If the add-in is listed in the Disabled section, got to enable the disabled add-in.

1. If the add-in is listed under Inactive, make sure "COM Add-ins" is selected in the "Manage" drop-down and click "Go...".

   

2. Check the checkbox next to the Add-in and click "OK."
   
   
3. Restart Outlook. Close Outlook, wait for 5-10 seconds, then start it again.

1. Select Disabled Items in the drop-down at the bottom of this window, next to the Go button.

   

2. Click Go.

   

3. Select the Add-in which you would like to re-enable.

   

4. Click Enable in the lower-left corner of this window.

   

5. Restart Outlook. Close Outlook, wait for 5-10 seconds, then start it again.

Enabling inactive/unloaded add-ins is trickier than enabling a disabled add-in. Normally, you should be able to enable them merely by marking the related checkbox in the COM Add-ins manager window (as in the above screenshot). In practice, Outlook may keep deactivating/unloading these add-ins whenever it restarts. Then you may need to look up for these entries in the registry:

1. Exit Outlook.

2. Run Regedit. Refer to How to open Registry Editor in Windows 10 for instructions on how to do so.
   Note: You need to have Administrator privileges to edit group policy and apply the registry changes.

3. In the registry editor, navigate to: HKEY_CURRENT_USER\Software\Microsoft\Office\Outlook\Addins\KoffAddIn.UserInterface

   1. Double-click "LoadBehavior" and change the Value data to "3."
      
      
   2. Copy the KoffAddIn.UserInterface add-in name.

4. Navigate to: HKEY_CURRENT_USER\Software\Microsoft\Office\x.0\Outlook\Resiliency\DoNotDisableAddinList

   1. Create a DWORD registry KEY: Click New (right-click on the blank space) and Select DWORD (32-bit) Value. 

      

   2. Give the newly created DWORD registry KEY the same name as that of the add-in you copied from the previous section (Step 3b), i.e., KoffAddIn.UserInterface.
      
      

   3. Double-click "KoffAddIn.UserInterface" and change the Value data to "1" to ask the system to always enable it.