I'm still on Sierra 10.12.6 and, after updating to Logic 10.4.2 from 10.4.1 my Faderport stopped working (same as when I updated to 10.4.1). Followed same approach as before (which had worked perfectly) by following this https://support.presonus.com/hc/en-us/articles/210040223
and installing the Faderport Classic. Was then prompted to update my firmware from v.1 to v.1.45 - followed the instructions but got a "Universal Control. The firmware update failed with error code 0x80004005.
After a few tries, and restarts, the Faderport still wouldn't show up. I gave up and installed it as a Mackie HUI and thankfully it is now working for me. I only use the main features so this is fine for now and at least I keep working :) Hopefully Presonus will sort this with a proper update, though as it's a legacy piece of kit? That shouldn't make any difference ;)
Know that doesn't answer the Mojave part but at least it's working for me in Logic. Good luck!