if it's allowed on the ssid, this is probably not a Meraki issue. Is the Client IP assignment set to Bridged or NAT?
If you are using NAT, the IP of the AP is used to make the accesses, so it may be that you have some blockage in the APs network.
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
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