I have IAP 215's setup with a Virtual Controller that I am trying to upgrade.
When I try to check for new firmware version I get the message "received no response from server". When I SSH into the controller and try to ping google.com I get unknown host, and I can ping 8.8.8.8.
I manually upgraded the AP's to 6.5.2.0 and still have the same issue after the upgrade is complete.
Also, I have another set of AP's, similar configuration and same version, I was able to do the check for new firmware and upgrade the AP's.
Figured out my issue -- Removed and Re-added the DNS settings to the AP