Subscription confusion

"My Subscriptions" shows that I'm a 5 year member until June 2024.  But when I try to access a new map layer it wants me to become a Premium subscriber.  When I click "Upgrade to Premium" on the My Subscriptions page it shows $39.99 less $20 coupon less $20.21 "prorated discount" for a total of $0.00.  But I can't actually pay $0.00! (and when I clicked "Pay Now" the button just disappeared and nothing else happened.  What's going on??  And how can I access additional map layers?