It sounds like you've done most of the prerequisites for linking Dynamics Sales to Outlook with the Dynamics 365 App for Outlook, but you're running into an issue when trying to add the app for a user.
The error message you're seeing ("Security Group Not Set") indicates that there may be an issue with the security group settings for the user. Here are a few things you can try to resolve this issue:
1. Make sure that the user is a member of the security group specified in the Dynamics 365 App for Outlook User role. You can check this by going to the user's record in Dynamics 365 and checking their security groups.
2. Try removing the user from the Dynamics 365 App for Outlook User role, and then re-adding them. This can sometimes reset any permissions or settings that may be causing the issue.
3. Make sure that the user has the necessary permissions to install and use the Dynamics 365 App for Outlook. This includes permissions to access and modify the user's mailbox and calendar, as well as permissions to install and manage apps in Outlook.
If none of these solutions work, you may want to consider reaching out to Microsoft support for further assistance. They can help you troubleshoot any issues with the app installation and ensure that all necessary settings are properly configured.
