I am on the same situation. Because i am new to Meraki and Fortigate(FG). I have NAT public IP of meraki cloud and open their ports on my Firewall.
My Client connect to the internet well but i cannot pick from which policy of my FG,but when i access blocked site i can pick up which policy blocks the apps and the devices accessing the site. On my firewall logs i cant locate Addresses or sources address of my client going succesfully to the internet.
Meraki Support has written back saying they can see the AP checked into the portal but there is failure to communicate with the cloud. I believe them because though i get to internet, i cannot ping the AP, but ARP and DNS are said to be fine.
One more thing i have realised even in the FG, if i switch off the policy for meraki, i still access the net but my setup is that everything through should go through the proxy. My boss do not like bypassing this proxy, this proxy is my Firewall again.
So my problem are in two parts: The AP and The FG. What policy are they using to access the net, how do clients access the Internet if i cannot ping this AP?