Just noticed this thread, so for the record:
I'm on Mojave 10.4.6 , and those 4 "modifier" keys on the left of the S1 do not work here neither.
Not that I would dearly miss that particular feature: My Apple Magic keyboard is placed just in Front of the S1, so I'm reaching those modifier keys quicker on the keyboard anyway. Also, from my old Digi 002 I'm already somewhat used to the fact that not all available buttons on Digidesign/Avid control surfaces are working.
(Sorry, couldn't resist!)
Nevertheless - Mojave is still supported with the latest PT release, so it would be cool if the same would apply to Eucon as well.