I know this is old, but I also had this issue. I updated my pool from 8.2.1 to 8.3 using the installer ISO. Both hosts came back up, I did an update on the pool master and then the slave, and now the slave has lost its network interfaces. In ifconfig, I see eth0, lo, and xenbro with no IP, along with a "xentemp" which has the IP address I assigned the management address. I did an xe-toolstack-restart and emergency network reset, which did not seem to help. xe pif-list, network-list and all other xe commands simply hang forever.

@scboley Yes, it's mostly just a matter of doing yum update: https://xcp-ng.org/docs/updates.html

Is the entire XCP-NG team employed by Vates?