This seems Like DNS related alert.
Following are the few troubleshooting steps I shall recommend.
Are you able to browse in Incongnito Mode?
Are you able to Ping Google?
Are the APs Live on the Dashboard?
Who is assigning IPs to the Client Devices ?
Are you able to resolve websites? nslookup
Verify DNS entries for a PC. Try to assign Google DNS?
Verify Firewall Rules.