membership registration simply not working for me at all

Hi, I have the Membership plugin installed and I’m sort of following this tutorial I came across to set up a membership subscription where paid users degrade to “free users” after X amount of time. I think I have everything set up correctly, but now that I’m trying to see if it all works, I can’t even get a registration to work.

On the registration page I created, I see the default unstyled subscribe form that is output by [subscriptionform], but when I enter data and submit, here is what happens:

I *briefly* see it flash to a page that looks like it has a UI to select a subscription type or something, but then the browser refreshes to the membership page again, only with everything unstyled, and the line “Nothing found. Oh, Sorry, no posts matched your criteria” in place of where the next step of the sign-up UI should be.

On the backend, I receive an email with credentials to log in (including a new password, even though I just selected one in the subscriptionform UI ???). If I try to login, the message returned is that the user is not active.

Can anyone help me out with what might be happening here? It sure seems REALLY broken to me, and I don’t even know where to start. I just assumed that the plugin would smoothly run a registration if you used the appropriate short codes in the right places…