One of the failures of a Perimeter 81 roll-out via Meraki firewall equipment is in VPN Routing. You will need to create each individual tunnel on Perimeter 81 for all offices/sites and then configure each of these tunnels using unique point information accordingly. This information would be acquired from the Meraki equipment. After which, you will need to complete all additional configurations at the main or tertiary points and ensure they are tested and access to all offices and/or resources test positive.
If you would like help rolling out Perimeter 81 on a Meraki network, we are happy to help. There is SO much frustration with these installations, but we have found solutions and are happy to share them with you.