This appears to be a common issue with Outlook 2016 and is system specific. If Outlook detects a plugin takes more than 1 second to load it may disable it.
In the case of the Vidyo Outlook plugin this may occur if the plugin did not authenticate as expected or took too long to reach the VidyoPortal.
Please check the Vidyo add-on settings and validate the username/password credentials. This will help to ensure fast load times.
If the issue persists you may choose to set Outlook to "Always enable" which prevent this issue from occurring.