So I know you posted this over a year ago, but just in case you never solved this, or for anyone else out there having the same issue, I have a fix. This seems to be mainly an issue with the Universal Control app and windows 10 users (which I am). Steps to fix:
1. Turn on your computer
2. Turn on your interface
3. Turn on your ADAT device
4. Open universal control app
5. Whatever sample rate your interface is set at, change it. Then, change it back again to your actual desired sample rate.
6. Congratulations, your ADAT inputs are now routed to your main mix output.