Error 404 on checkout

Hello,
I get a 404 error page on checkout once globalpay is selected as the payment option.
Initially I thought it was plugin related or cache related, but after disabling all plugins, clearing cache and even updating permalinks, the problem persisted.
So on a hunch I set the Globalpay to Test Mode and surprisingly the transaction went through to globalpay.
Resetting the store to Live Mode results in the process failing again.
I think it is somehow related to the Live Settings of the plugin.

Can you help out here?
Thanks

https://www.ads-software.com/plugins/woocommerce-globalpay/