The protocols that configure port forwarding automatically are either not available or have failed. UPnP and NATPMP are not functioning in your router as Roon expects.
Try the below steps, and let me know if anything changes:
Turn on UPnP on your router and try to run Roon's port forwarding test again.
Try to set up manual port forwarding in your router.
Make sure the IP/Port matches in any port forwarding rule you create.
Double-check to make sure you don't have any VPNs, Firewalls, or other network filtering software blocking Roon.
Check if your modem is in Bridge mode.
Restart your network hardware and update firmware.
If none of the above help, you can also explore using Tailscale rather than port forwarding, here’s more info:
Universal Plug and Play (UPnP) is a series of protocols for communication between networked devices. It allows for devices to automatically discover, create connections and communicate with each other without additional setup. UPnP is the networking equivalent of Plug and Play which is used for devices like keyboards and other peripherals that are used with client devices today.
UPnP on the Meraki platform is not supported at this time. However, since the standard uses protocols like TCP, UDP, IP, HTTP, and XML, the MX and/or Z1 can pass UPnP traffic within the same broadcast domain (VLAN or subnet). This means UPnP enabled devices will be able to communicate with each other when on the same VLAN/subnet behind the MX/Z1 gateway. If the UPnP devices reside on different VLANs/subnets, they will not be able to communicate because the MX/Z1 does not forward broadcasts between VLANs.
Given the SMB/enterprise nature of the Meraki product line, I am not sure if a standard solution can be found that is similar to those used in residential routers.
Have you tried using @benjamin’s Tailscale recommendation?
This thread will automatically close since it hasn’t received a response from the OP. We’ve concluded that the router you’re describing doesn’t support plug-and-play configuration of port forwarding - you’ll need to instead try Tailscale.