How do I set Membership to allow a Member to escalate themselves?

So, first, I'm new. And this is probably just a setting, but I can't figure it out. (so, I haven't broken an existing thing -- I appear to have misconfigured a new one).

In Membership, I have three Access Levels:

* Visitor
* Registered User
* Paid User

A VISITOR is supposed to be just some unidentified visitor.

A REGISTERED USER is supposed to be someone who has registered an account on the WP site, but hasn't paid cash to be a paid user.

A PAID USER has paid some sort of money to be a subscriber. The amount of money varies based on their subscription plan.

I use the Visitor/Registered User/Paid User short-tags in combination with the Pay-Per-View plug-in to feed content to people, priced in accordance with their condition.

That seems to work.

So, then I have to establish a way for them to escalate from Registered User to Paid User.

This is where I'm stumbling.

I have five Subscription Plans:

* The Lunar Pass (a 1-month pass)
* The Solar Pass (a 1-year pass)
* The Spinner Pass (a 1-day pass)
* The Universal Pass (a lifetime pass)
* Walker (a subscription plan I thought I needed to have extant to support users who are registered, but who have not paid. Do I really need this?)

The only difference functionally between the Subscription Plans are the prices and the length of the subscription. The result of every Subscription Plan (except Walker) is that the User now is a PAID USER for some set period of time.

So...

I have a Subscription page, where I've place [renewform].

If I log out, and look at my subscription plan, I am told "You are not currently logged in. Please login to view your subscriptions."

Okay, that makes sense.

So, I create a new account ("Fishy"). I log in. My new member registers as Fishy, with a Membership Level of "Registered User" and a Subscription Plan of "Walker".

I navigate to my PPV page and my product is now marginally cheaper (which is as it should be).

HOWEVER...

I navigate to my Subscriptions page to upgrade myself and [renewform] produces output like this:

Your current subscriptions are listed here. You can renew, cancel or upgrade your subscriptions by using the forms below.

Walker

You are on an indefinite membership.

Upgrade from Walker

Move to : The Spinner Pass

For 24 hours, enjoy our premium content. This is the most bottom-line economical.

Move to : The Lunar Pass

For one calendar month, enjoy access to our entire library and any new premium content produced.

Move to : The Solar Pass

Perfect for planets with dreary seasons, a Solar Pass is good for an entire year.

Move to : The Universal Pass

The ultimate expression of love without needing a shower afterwards — the Universal Pass offers you access to all our premium content for as long as you exist in solid form.

However, there are no actual links!

There is no Subscription Price Text. There is no Price. there is no "Sign up" link.

What should I be doing to have a user be able to upgrade to a subscription plan, becoming a PAID USER for the specified period of time?

What troubleshooting steps might I take to proceed?

Thank you!

Edward