PayPal stuck in sandbox mode in lMembership2 Pro

Regarding http://brainenergysupportteam.org

When someone wants to become a member the payment button is a PayPal sandbox button and goes nowhere. The process use to work. Now it doesn't. I have searched the support forums, triple-checked my settings, disabled plugins and reactivated them, and I am at a loss.

Also, does the recurring payment automatically charge the credit card or paypal account on a regular basis or just send a reminder? This is not clear in the setup or the WPMUDEV documentation for this plugin.

As an aside, it would also be helpful if the date of the question/discussion were displayed without having to open the thread to find out it's two or more years old.