Follow the steps in the tab you opened earlier; ignore steps 3 & 7.
In Proxmox: change the SCSI controller type on the VM to LSI 53C895A; set RAM to no less than 2GB; set CPU to 2 cores, or more; disable the Guest Agent.
As of June 2019, you probably need the newer controller software to handle 802.11ax APs. Please follow the upgrade guide on that.
Side notes
As of June 2019, it appears that the 802.11ax APs support IPv4 + IPv6 as standalone; but the ezMaster system is IPv4-based, and currently runs on a locked-down Debian 6 stack.
The admin password for the APs, is separate from the ezMaster admin login; but you can update the APs login from the ezMaster admin. I think this is because you can ultimately use ezMaster to manage multiple networks as a MSP.