Its not a good idea to have availability running via the Admin port - it should always be via the same port that is used by the APs to connect to the controller = if APs connect via ESA0 then use that for availability or that could result in false positives.
Another KB about the admin port - in short don't use it - just for the initial config....
https://gtacknowledge.extremenetworks.com/articles/Q_A/Should-the-Admin-port-on-an-IdentiFi-wireless...
Back to the issue - are the Admin ports in the same VLAN/subnet ?
If not did you set a default gateway in the GUI > Controller > Administration > Host Attributes > default gateway