Have a Cisco Meraki that's behind a Palo Alto Networks Firewall, unable to connect the Meraki to the Dashboard for updates or to make changes to the configuration. Only have one Public IP Address that's currently on the Palo Alto FW as it's the gateway, and planned on only using the MX for WiFi and switching. Not sure if anyone has a way of connecting the MX to the Dashboard ot get updates while leaving the PA in line.
On your Meraki Dashboard, if you hit the question mark in the top right corner, you'll see a link to Firewall Info.
This will show you all the relevant IP Addesses and ports on upstream firewalls, neccessary for proper Merak Cloud connectivity.
These openings are different network to network/organization to organization, and may be subject to change, depending on which products you have in the Dashbaord. E.g. If you have Meraki Cameras, you'll see entries in the list for IPs and Ports required by the MV Cameras.
You should lean towards what your own Dashboard informs you of neccessary IPs and Port openings.
Tldr; make sure udp/7351, udp/9350-9351 and tcp/443 are open outbound from the Meraki MX, as well as ICMP...