I have a test user who is a member of an Active Directory Security Group. I've added that Active Directory group to the a SharePoint Group "[SiteName] Users".
In this scenario, when I attempt to login with the test user it says "This site has not been shared with you." Under site permissions when I hit "Check Permissions" and input the test user's username, it says it has the correct permissions granted by the correct groups.
And when I add the test user directly to the SharePoint group, it works fine - the user can login and has the correct permissions. Hitting "check permissions" shows the same output as when only the Active Directory group is added to the SharePoint group.
Am I setting this up incorrectly or need to do something else?