I have also not been able to get my Heusinkveld sequential to function, it is also map-able but does not work in game. I have been also having a hard time getting my DD2 to map under a custom profile I saw some of the PC2 work-arounds offered, but none seemed to work right off the bat.
Considering everything works in every other title (Rfactor 2, AMS, AC, ACC, KartKraft, Dirt...) I wasn't inclined to dig too deep to make it work considering it was in EA, until today. Since the update did nothing to fix this I was planning on asking this very question here as well.
Gear:
Fanatec DD2, Huesinkveld Sprint pedals, Huesinkveld Sequential
Edit: Update, I decided to give another attempt at "just try it again" and this time when I selected the custom profile it allowed me to successfully map the steering direction to the wheel input. After that I went ahead and assigned all my buttons like I did in EA, same as all the other titles more or less, including the sequential to the shift commands. This time when I went on track.. magic! The formula classic cars are begging for a shifter, super stoked!
I felt it was always the Fanatec profile was anticipating a particular input type, and was never able get the custom profile to work before.
Sadly, maybe, just try it again. Note: I deleted nothing, did not reinstall, did not alter or add any additional profiles besides what the game generated.