@llyons - check out this thread: Missing data on host's "Last Report" column - Foreman 3.0
I know I gave up and re-installed a few different times and found out that for whatever reason, the 3.x series required the following flags to be set on the installer:
--puppet-server-foreman-ssl-ca "/etc/pki/katello/puppet/puppet_client_ca.crt" \
--puppet-server-foreman-ssl-cert "/etc/pki/katello/puppet/puppet_client.crt" \
--puppet-server-foreman-ssl-key "/etc/pki/katello/puppet/puppet_client.key"
Hopefully this solves it for you. In the end, I’m not going to use Katello since I have a smaller number of nodes to manage so I’m not running into this problem anymore. I’m testing out the puppet_os_patching module with some other customizations so I can patch when needed.