a few scenes were blank for me too, maybe they're unfinished? i dont know for sure
If you meant, like, a good portion of scenes (mainly later in the game), and not *literally* every single sex scene, then that's because the scene itself has been written and implemented, but the artwork / CG / animations haven't been finished yet. Ex. Right now, the 6th domain has a lot of scenes written out, but most of them are blacked out since the Domain itself is still being tweaked, and the artwork is still being made.
If literally all of the scenes are blacked out, though, then that's probably a bug. The game's Discord does have a bug reports section in it where people will be able to help you out (or someone else may have already run into the issue and solved it!). They're super helpful over there and should be able to get you sorted out. Be sure to take a look at the bug reporting guide at the top of that channel to make it clear and easy for others to help you solve the issue if you do end up submitted a report!