When using a Conditional Access policy to block all other devices (except for Android, iOS, Windows Phone, Windows and macOS), the policy blocks the connection with the below message because the authentication sign-in log has no device visible.
"Your sign-in was successful, but does not meet the criteria to access this resource. For example, you might be signing in from a browser, app or location that is restricted by your admin."

It is possible to exclude the user who is initiating the request but that would allow non-supported devices from making Azure Connections using the Graph API. Which is not an option.
AB#7387