I observed this issue with v7.10rc3 and do not know if it applies to other versions. The ax^3 is configured as an AP directly (no capsman).
I added a device to my world that required a 2.4G wifi which I already had configured on the ax^3. The device would connect and disconnect 2 seconds later. It never got to the point of asking for an IP address. I simplified the configuration to reference a security profile with nothing but the passphrase, no channel profile, and a data path profile. It still would not stay connected for more than 2 seconds. I then changed the configuration to not use the security profile and instead put the passphrase directly in the configuration. That solved the problem and the device connected. In hindsight, with the same ROS version, a few days ago I could not connect an android phone to the same SSID on the ax^3 which had the original configuration. I did not investigate that further but suspect it was the same issue.