Woocommerce Checkout Not Processing

After installing Quadpay on our website, it worked for one day. Today, when a customer tried to checkout, they received the following message:

Sorry, there was a problem preparing your payment. Please try again.

We tried to run a test purchase and received the same message. In the past 2 hours, two more customers received the same message and ended up abandoning their orders.

This is alarming, please help ASAP!

Everything is setup correctly, we are live and everything was working yesterday. Not updates, new plugins or anything else was introduced between yesterday and today.

Thank you