WooCommerce Multi Currency not working

I have had to turn off the premium version of the WooCommerce Multi Currency Plugin as it is interfering with the product prices displayed on the basket and checkout pages. We only noticed the issue when a customer placed an order from Australia and paid in USD. They ordered 2 yards of fabric but the price they were charged was for just 1 yard of fabric. My customer was also not charged for shipping and the shipping options were not visible to choose from.

My web developers recommended that I disable the plugin for a few days so that we could confirm that it definitely is the plugin that is causing the issue. They updated the plugin manually to the latest version but it did not fix the pricing issue. It actually created a new issue/conflict with something else on the site, breaking the javascript (meaning that users can’t use the tabs on the side of the screen to change currency).

I’m also not able to use the automatic updates feature for this plugin when I enter the purchase code/licence key in the ‘Auto update key’ box on the plugin’s ‘Updates’ page. Is there a way to fix this too? It says that my key expired on 11 January 2019 and I can only update the plugin manually.