Obligatory question every time this comes up. How do you think this works? How are you trying to use it?

Because the only way that this works is if you get a text for a code, and when you go to use the code, your keyboard pops up with the “AutoFill from Messages” option, and you click it.

I know it says it right there on the screen, but this always needs clarification that you HAVE to use AutoFill.