Since Office 2013, Outlook has introduced a security measure that automatically disables add-ins with an extended startup time. However, this startup time is set so low that issues may arise if an add-in is developed in .NET instead of C++, as .NET requires loading additional background data by default.
To avoid this, you can configure a group policy that adds the add-in to the "DoNotDisableAddinList" key in the registry. This will ensure that the add-in is not disabled on slow computers or in situations where startup may hang.
The value should be added to the "HKEY_CURRENT_USER\Software\Microsoft\Office\x.0\Outlook\Resiliency\DoNotDisableAddinList" key, where "x.0" is the Outlook version, e.g., 16.0 for Outlook 2016/Outlook for 365.
The value to be added is a DWORD value with the name "CateringPortal" without the quotation marks.
The value's data should be set to 0x00000001 (1)
Once this is rolled out, the add-in should be protected against automatic deactivation by Outlook.
For more information, you can refer to Microsoft's own article on the topic, available here: