While devices will primarily connect to Dashboard using UDP port 7351 for their tunnel, they will attempt to use HTTP/HTTPS if unable to connect over port 7351. When devices are operating like this, a message will be displayed on the device's status page indicating that the 'Connection to the Cisco Meraki Cloud is using the backup Cloud connection.' If this is observed, please ensure that port 7351 is being allowed outbound through the firewall or security appliance traffic from the Cisco Meraki devices will pass through.
Okay, that makes sense because currently the MG21 is connected to a switch and the ingress interface for that VLAN is currently shutdown and has been for days. However, the cellular side was fine yesterday but today I cannot ping the internet from the MG21.