Plugin causing error with shipping options

Hi there, whenever this plugin is activated when people try to checkout they get this message

“There are no shipping options available. Please ensure that your address has been entered correctly, or contact us if you need any help”

All of the shipping methods are set up correctly for these customers locations, and it is only when the plugin is activated.
Can you please advise on how we can resolve this.

The page I need help with: [log in to see the link]