I think I know what I did first time around that failed the install. Under “1. Enable the EPEL and Software Collections repositories:” I only ran the “CentOS 6/7: sudo yum install epel-release centos-release-scl” and skipped the RHEL7 section to install “sudo yum install https://dl.fedoraproject.org/pub/epel/epel-release-latest-7.noarch.rpm”. Since I’m installing on CentOS I didn’t think I needed to run something that was tagged only for RHEL 7.
That should probably be changed to “CentOS/RHEL 7” like it is under " 2. Add Open OnDemand’s repository hosted by the Ohio Supercomputer Center:"
I verified this with another fresh install, the install OnDemand fails if you don’t install the RHEL EPEL release.