I had the same problem; my 1810c interface was not showing up in the drop down menu for "configure audio device" in Studio One 4 Pro.
It turned out that I needed to click on "Studio USB" from the drop down menu -and it worked! Studio One then recognized the 1810c. The solution was embarrassingly simple. Basically just try some of the other options in the drop down menu and see if they work -even if it's not specifically naming your interface ;)
If you're still stuck after looking through all these pages, you can "create a ticket" in the "support" tab in the My.PreSonus page and ask an expert about your problem. They were really patient and thorough -but definitely give things a try yourself first.
He suggested making sure my antivirus systems (Avast and CCleaner) were allowing the drivers in Universal Control to connect to Studio One by either uninstalling those programs, or whitelisting Studio One and Universal Control:
Also, I found this article on Sweetwater's website that has a lot of different troubleshooting things to try if your DAW isn't recognizing your interface:
(but it ended up being much simpler than that, of course).