In the Datacenter we have the MX250 in NAT mode, with the Internet1 port connected to ISP with internet (with access to the Meraki dashboard), and the Internet2 port connected to ISP with MPLS only.
In the branch it is the same, we have the MX67 in NAT mode, with the Internet port connected to ISP with internet (with access to the Meraki board), and port2 (setting as uplink) connected to ISP with MPLS.
Through the Internet link, the MX devices connect and registry to the dashboard and build VPN, but the MPLS link no found, the port status is "Failed" on both sites:
The transport on the MPLS link was tested, the connectivity is sussesfully.
What configuration do you recommend to provide the 2 operational uplinks (Internet and MPLS)?
Note that the diagram shows the MX in VPN concentrator mode. It is possible to make this work in NAT mode as well, but you need an additional firewall or something else to provide Internet Access for the MPLS network.
Had a similar issue and the MPLS had no internet exit so there is a 3rd way as well, you can participate in the Beta version which will help over the issue. You will have to call Meraki TAC to be able to get this working and register for the Beta version. The Beta works, just not publicly released because they are still testing it across the million scenarios at user production.