We experienced a network failure, which knocked off a few of the XenServer hosts. After performing the triage work, I began reviewing the XenServer hosts to make sure they were up. Of the 4 servers in one pool, 1 was experiencing an error, which I hadn't seen before: "Xenhost still booting". This meant the 3rd host was stuck in the emergency maintenance mode, and for some reason, I couldn't get it out of the mode. I had to take the following steps to correct the issue:

1. I started by making sure that the all hosts had xapi running on all hosts.
2. From there, I issued the following command "xe pool-emergency-transition-to-master".

Once I did this, the host synced with the master and the problem was resolved!