Marketpress and Events + Not Working

I am using marketpress and events+ for users to register for events. when a user tries to register for an event they are not being taken to the cart/checkout process.

After I click "register now" on the event page I see the message "You haven't paid for this event. Please select your membership level below." There is nothing to select below and the error: Warning: Cannot modify header information - headers already sent by (output started at /home/content/35/11098935/html/wp-content/themes/genesis/lib/structure/header.php:63) in /wp-content/plugins/marketpress/includes/common/class-mp-cart.php on line 2034. when I try to click the "checkout" or "click here to purchase your ticket" link the page refreshes and nothing happens.

This was working fine before i updated Marketpress and events+. Please advise...