Reminder: If You Can’t Upgrade Your ESXi Host, It Might Be Because You Need to Remove It From The Cluster First

After you’re done freaking out that you can’t upgrade your ESXi host (from 6.5 to 6.7 in this particular case – but likely similar across the board with 5.5 and 5.1) you need to remove it from the cluster.

1. Enter Maintenance mode and Flush VMs.
2. Remove from Cluster
3. Upgrade