I seem to be having the same problem that many other people have had, but their solutions are not working for me.
I read this post and its solution. My problem, I think, is that my pop-up is being called from my header, another reusable element, which is then called from the index page.
Interestingly, this is the default way that the Bubble assistant had it set up.
What else can I try to make sure the users are forced to login or sign up??