Have you configured the MX to use the WAN port that the Internet is connected to as its primary WAN link? https://documentation.meraki.com/MX/Firewall_and_Traffic_Shaping/MX_Load_Balancing_and_Flow_Preferences#Flow_Preferences    If you are plugging in an Ethernet based Internet circuit is it using auto/auto for its speed and duplex, and if not, have you matched it correctly on the MX WAN interface? ... View more