This articles describes solutions to enable add-ins that are marked as inactive in Outlook but they are NOT marked as disabled. Outlook 2010 and Outlook 2013 actually have 3 status labels for add-ins: enabled, disabled and inactive. Most people confuse an inactive add-in with a disabled add-in, but they are not really the same thing.
Sometimes, it may happen that Outlook deactivates an add-in (or all your add-ins) without marking it as being disabled. For example, if you run the Outlook Product Stability Tool, it may end up making all your Outlook add-ins inactive, but at the same time they are not listed in the Disabled Items list.
If you open the COM Add-ins manager (by clicking on the Manage COM add-ins “Go” button, in the above screenshot), these inactive add-ins are not marked as being enabled, but they are also not marked as being disabled. In fact, their “Load Behavior” is set to “Unloaded”:
Enabling inactive / unloaded add-ins is trickier than enabling a disabled add-in. Normally, you should be able to enable them simply by marking the related check-box in the COM Add-ins manager window (as in the above screenshot or as detailed in this Disabled Add-ins tutorial). In practice, Outlook may keep deactivating / unloading these add-ins every time when it restarts…
Enabling inactive Outlook add-ins that keep being unloaded
If Outlook keeps deactivating an add-in, first of all try to uninstall & reinstall the given add-in. If it doesn’t solve the issue and the add-in is still being displayed as inactive, please follow these steps to activate the add-in:
1. exit Outlook and uninstall the given Outlook add-in from your Windows Control Panel (see Add/Remove Programs or Uninstall Programs, depending on your Windows version);
2. open your Windows registry (run regedit.exe) and locate the following registry entries:
HKEY_CURRENT_USER\Software\Microsoft\Office\15.0\Outlook\Resiliency (replace 15.0 with your actual Outlook version: 15.0 means Outlook 2013, 14.0 means Outlook 2010, 13.0 means Outlook 2007, etc) – remove the REG_BINARY keys found in DisabledItems and CrashingAddinList:
HKEY_CURRENT_USER\Software\Microsoft\Office\Outlook\Addins – remove the keys that refer to your troubled Outlook add-in. If you want to fix the OneNote Outlook add-in, remove the entry named OneNote.OutlookAddin.
3. reinstall the related Outlook add-in and restart Outlook: it should be loading fine now, without being listed as an inactive add-in.