To prevent the add-in from disabling itself, you can place it in the "Always Enable" list. When using Covideo for Outlook, users can force the add-in always to be enabled.

Step 1. On the File tab, click <Slow and Disabled COM Add-ins>.

Find Covideo for Outlook.

Step 2. Click "Always enable this add-in”

Step 3. Restart Outlook for all of the changes to take place.

Outlook will try to protect the user experience by disabling add-ins that it considers to be misbehaving or if there had been an update. This will cause the add-in to disappear from the toolbar. 

Here are the steps to re-enabling your disabled add-in:

Step 1. In Outlook, click on "File>Options>Add-Ins>Go..."

 Step 2. Once you click "Go..."

Make sure Covideo for Outlook is checked. Click "Ok" when done. 

Step 3. Restart Outlook to apply changes