Extreme Networks Cloud IQ onboarding of switches is quite straight forward and can be really useful for zero touch provisioning.
A few places to check if having problems connecting to Cloud IQ.
Add the correct device type and its serial number into Cloud IQ.
On the switch make sure it has the correct time otherwise it may have problems connecting to the server.
Enable DNS client on the switch so that the iqagent can resolve the FQDN of the server.
Make sure the switch can reach the internet and any Firewalls are not blocking the traffic.
Firewall Configuration Guides: