If the Juno DI line outs are connected to the 4i4 Line Ins, you should hear sound in the headphones of the 4i4. (first test)

Then you need to make sure you have MIDI out from the Juno Di to the Focusrite so you can send MIDI thru along with the audio (which should already be going from the Juno to PT via the 4i4 judging from your description).
You'll likely want MIDI out from 4i4 to the MIDI In on the Juno also, at least I would.


Audio and MIDI are separate.
Lastly to hear the audio in PT you may need to visit the Audio Driver screen and make sure you have the right inputs/outputs selected for the 4i4.

Once you get it all set up right I think you'll be happy.
I use a 2i2 and 18i20 regularly.

I do not work here, but the benefits are still awesome
Make your sound your own!