Woocommerce Order Processing Error

A client site of mine, when an order is processed instead of taking users to an “order received page” but instead it shows this:

{"result":"failure","messages":"
\n\t\t\t
Sorry, your session has expired. Return to homepage<\/a><\/li>\n\t\t\t
Country<\/strong> is a required field.<\/li>\n\t\t\t
First Name<\/strong> is a required field.<\/li>\n\t\t\t
Last Name<\/strong> is a required field.<\/li>\n\t\t\t
Address<\/strong> is a required field.<\/li>\n\t\t\t
Town \/ City<\/strong> is a required field.<\/li>\n\t\t\t
State<\/strong> is a required field.<\/li>\n\t\t\t
Zip<\/strong> is a required field.<\/li>\n\t\t\t
Email Address<\/strong> is a required field.<\/li>\n\t\t\t
Phone<\/strong> is a required field.<\/li>\n\t<\/ul>","refresh":"false","reload":"false"}

Woocommerce is up to date, and all add on plugins are also up to date. Please help.