I'm sorry for the trouble. Steam can finicky and we did have to update it a few times in a row to fix somethings when Step 4 launched which can confuse it. Can you try uninstalling the game, clearing your download/upload cache, and then try reinstalling? Sometimes that gets Steam to notice there's more to update. Waiting a few days and then uninstalling/reinstalling can also sometimes get it to go away.
You could also download the free main game here from Itch just to try it out and see if Step 4 works for you when you get that build.