Ensure the client certificate and intermediate CA are valid and not expired. Check that the SSID is configured for WPA2-Enterprise with EAP-TLS.
Check Meraki Event Logs under Dashboard → Wireless → Event Log and Look for EAP failure reason.
I am not a Cisco Meraki employee. My suggestions are based on documentation of Meraki best practices and day-to-day experience.
Please, if this post was useful, leave your kudos and mark it as solved.