You need to check the local status page to see why it says there is a problem. https://documentation.meraki.com/zGeneral_Administration/Tools_and_Troubleshooting/Using_the_Cisco_Meraki_Device_Local_Status_Page#MX_Series_with_Single_Dedicated_WAN_Link ... View more

Check the speed and duplex of the MX-64 uplink.   It should show 1Gbps Duplex Auto. You can then look closely to see if it auto negotiates to Full duplex or not.   You can also look at the Event log for flapping ports, CRC errors, collisions, or other type of errors too. ... View more

Thank you for giving this information. ... View more