@Jame Apple has been working on remote management for a long time and works with MDM developers. I get the feeling that Microsoft is a wee bit behind. I haven't tried administering windows device using SM however sicne Meraki support it I would log a support case and see if they can figure whats going wrong.
Also IMHO the logs for SM are not helpful one bit when it comes to troubleshooting, I have often seen the logs simply report "error"
Good luck!