Is the AP plugged into a port where it can successfully grab a DHCP IP address automatically? If you plug a laptop into the same switchport where you would plug in the AP, and run an ipconfig command, you're getting an IP address? Or do you need to configure a static IP address on the AP? You can also associated to any SSID on the AP and point a browser to ap.meraki.com to get to the local status page on the AP and maybe get an idea if it's trying to connect to the cloud. More info here https://documentation.meraki.com/zGeneral_Administration/Tools_and_Troubleshooting/Using_the_Cisco_M...
Does your firewall allow outbound traffic in general? If so, Meraki equipment is pretty much plug and play, and all connections for Meraki cloud communications will be initiated outbound from the AP. It's generally only when you're on a LAN behind a very restrictive firewall or proxy environment that you may need to go to Help > Firewall Rules as @MRCUR mentioned. If that's the case, and your firewall is even blocking outbound connections, you would have to put in outbound firewall rules, for example UDP/7351 for Dashboard communications, TCP/7734 for firmware and configuration downloads, etc. Or if you're behind a web proxy, using the local status page I mentioned above, there is a configuration option to input proxy credentials, so the AP could make a backup cloud connection via a proxy.
You could circle back with Support (just respond to the most recent email, even if the case was closed) and ask for assistance with some of this local status/config troubleshooting. Also, if it's definitely firewall related, maybe if it's possible as a temporary test, whitelist the AP's IP address with an allow any/any/any rule just to make sure the AP fully comes online in Dashboard, just to prove it out, and then you would know it's just a matter of firewall rule updates.