Membership Plugin Subscription Failed

I have set up the membership plugin and setup some subscriptions. Just yesterday I had two new customers sign up under a subscription package.

The first had no problem. Their card was charged and their subscription was added to the website and through as an automatic subscription.

The second client put in their card information and clicked process card. The got a message that their subscription was unable to be added and went back to the page where they enter their info and payment info. It didn't create a subscription on the site and didn't create an automatic subscription on but it did charge their card.

So I thought maybe it was something wrong with that specific subscription. So I logged on and subscribed under that subscription with my own account and card. It worked perfectly in every way.

Please advice as what the problem could be and how to fix it.