Did you downgrade your script extender to v30? BG3SX doesn't work with BG3SE over v30. If you want to use BG3SX, you have to downgrade your script extender to version 30. And since you can't manually download v30 anymore, you have to do it via the mod manager.
Go into your BG3MM, at the top go to Settings -> Open Preferences. At the top, select Script Extender, and check the box that says, "Enable Developer Mode". A new tab will appear that says, "Updater". Go there, under Update Channel, select Release (if it's not already on it), then just below that where it says Select Version, change it to version 30 (30.0.0.0.0 whatever the last v30 version is).
Then close that out, go up to the top where it says Go, and select Launch game. It will auto download v30 and install it. Now all your sex stuff "should" work just fine.
On a side note, if you're going to launch your game from the BG3MM, make sure you go to your Settings -> Preferences, and under General, make sure you have the box that says "DirectX 11" checked. Otherwise, it will launch the game in Vulcan, and that sucks lol.