Not sure. When we installed the XCP-ng system and logged into the IP from a browser the first thing that popped up was to install the XOA VM. That's what we're using.

Oddly, sometimes it connects and other times we get that error that it's throwing a tantrum.

No, we're using the free version.

@DustinB
As stated, I reassigned the IP to an address I couldn't ping (192.9.91.9). So, no, there are no other devices on the LAN with the same address.