Two permissions exist in the Membership Plans group of a user role:

• List Membership Plans — required to see the menu entry and open the list page. Without it the page redirects to the admin dashboard.
• Edit Membership Plans — required to open the New Plan / Edit Plan form and save changes. Without it the form redirects to the admin dashboard.

There is no module or Sprwt plan requirement for the Membership Plans pages themselves. Assign the permissions under Business Settings > User Roles.