I tried my suggestion before posting and it worked for my theme. I’ve just had a look round the internet and other pundits are offering the same fix for this question, and no other fixes.
I was unable to get to your WooCommerce checkout page to be able to take a look. I added-to-cart but was taken to another site for checkout. Is it possible to have a look at your WooCommerce checkout page?
Do you have any caching on the checkout page?
Could you try the conflict test. Temporarily deactivate all other plugins except WooCommerce and switch to the Storefront theme. It should work now? If so, reactivate one-by-one and test to try to identify which software element is preventing the default behaviour.
Its possible your theme is using its own checkout page template. You can check at:
Dashboard > WooCommerce > Status > Overrides section at the bottom. As its a commercial theme I don’t have access to it. If the above get nowhere, you could ask your theme support service for advice, mentioning that you have already set a null t&c page.