When starting, Outlook allows a set amount of time for each third-party add-in to start. If the add-in exceeds that time, it is automatically disabled. The timeout is applied regardless of whether the add-in is starting correctly or not.
When this happens, Outlook displays a warning message that an add-in has been disabled. Click View Disabled Add-ins... . If the problem add-in is the Avaya IP Office Plug-in, click on Always enable this add-in.
If you suspect this has happened but you did not follow the warning message link above, you can enable the add-in through the Outlook menus as follows:
To enable the plug-in:
1.In Outlook, select File | Options. Select Add-Ins. The Avaya IP Office Plug-in appears in the list of Inactive Application Add-ins.
2.Click Add-in Options. From the Manage drop-down, select Com-Add-ins and click Go.
3.In the add-in, select Avaya IP Office Plug-in.