Hi Kristey,
To set up the TimeCore as an RTP-MIDI session participant, make sure to not only select 'participant' in the TimeCore's web interface, but also set the session name to what you have configured under 'Bonjour name' of the session in the MIDI Network Setup on your Mac.
After a few seconds of waiting, you should see it arrive in the list of participants.
Also, of course, make sure the TimeCore and the RTP-MIDI host are in the same (sub)net(work) (or have the correct access to each other)
If the information above is insufficient to make this work, drop us a line via email on support [at] visualproductions [dot] nl.
Cheers,