@HMHK This seems to be normal behaviour. I spent months talking to support about this involving our firewall vendor as well. The agent uses port 993 which is IMAP usually, I dont think firewalls seem to like the Meraki client because of this.
After spending almost 4 months going backwards and forwards we ended up dropping SM for our Mac clients in favour of JAMF. I know others in the forum have done the same.
SM works perfectly with our iOS devices its only MacOS devices that were affected.