When you click the Dynamics 365 app in Outlook (anywhere the app is supported) and your Dynamics 365 (online) instance is version 9.x, you see the following message:
“Sorry, something went wrong while initializing the app. Please try again, or restart the app”
When you click View More, you see the following additional details:
"Error: AppforOutlookModule was not found, empty appId returned Trace: Error: AppforOutlookModule was not found, empty appId returned at ..."
This can occur if you have a custom Dynamics 365 security role assigned and the role does not include Create and Write access to the App entity.
To work around this issue, you can grant the Write and Create privileges to the App entity. A user with the System Administrator role can access and modify security roles by navigating to Settings and then clicking Security. Within the Security area, click Security Roles. These privileges are located on the Customization tab of a Dynamics 365 security role.
Microsoft is aware of this issue and is investigating other potential fixes.