Membership does not show upgrade button/link.

I have three access levels set.
Visitors (no access to protected content)
Level 1 is free (Level 1 protected content)
Level 2 is paid (Level 2 protected content)

a) When I set membership use subscription to "none" and I try to register as a user, I have no access to (Level 1 protected content) even if I enroll in Level 1.
I see both subscriptions Level 1 and Level 2 but the Level 1 subscribe button takes me nowhere and I remain a visitor.

b) When I set membership use subscription to "Level 1" and I try to register as a user, I automatically become a member of Level 1 and I also have access to (Level 1 protected content).
I see Level 2 subscriptions but the Level 2 subscribe button is missing. So there is no way to upgrade.

What I want is for the subscribers to automatically become members of Level 2 and have the option to upgrade to Level 2 at their leisure.