First, please make sure you are using the latest version of the app - 2.4.4. There was a recent version that had a bug with recognizing inputs.
There have been user reports in the past of Ableton interfering with other apps using MIDI interfaces. I would recommend temporarily disabling Ableton to see if that could be causing the issue.
I just checked and I am using version 2.4.4. I also tried both quitting Ableton, as well as restarting my computer, and unfortunately none of my midi interfaces are showing up in the menu. Is there a solution with Audio/Midi. I'm on a mac running 10.13.6
I just tested Version 2.4.4 on MacOS with several MIDI devices, and it seems to be working perfectly on a couple different computers. I wish there were more I could do, but without having your hardware on hand, I'm not sure if there is anything I can do to further help with this at this time.
If your interfaces are standard MIDI devices, they should connect to SeeMusic. The issue would most likely be with the system or another app interfering with the signal being transmitted to SeeMusic.
Can you record the MIDI outside of SeeMusic in Ableton or another app, and then import the MIDI file to SeeMusic to make your video?