The API you're looking for in particular is https://developer.cisco.com/meraki/api-v1/#!update-device-management-interface and will give you a query something like this (this is using dual WAN on an MX64): PUT /api/v1/devices/[SERIAL NUMBER]/managementInterface {"wan1":{"wanEnabled":"enabled","usingStaticIp":false,"vlan":null},"wan2":{"wanEnabled":"enabled","usingStaticIp":false,"vlan":null},"ddnsHostnames":{"activeDdnsHostname":"[NETWORK_NAME]-wired-[GENERATED-NAME].dynamic-m.com","ddnsHostnameWan1":"[NETWORK_NAME]-wired-[GENERATED-NAME]-1.dynamic-m.com","ddnsHostnameWan2":"[NETWORK_NAME]-wired-[GENERATED-NAME]-2.dynamic-m.com"}} ... View more

I got a reply around 9:30 PM EST on my case indicating that it was fixed. ... View more

Just as an addendum to this, we were able to enable our interfaces via API calls. ... View more

We started getting the same issue when trying to re-enable a WAN1 interface on an MX. Gives the error "Must be blank or an integer between 1 and 4094 inclusive.", and it won't let you save if you leave it blank.  ... View more