One more clue. This WooCommerce doc also says “View the XHR tab on your browser’s developer console and look at the response. The expected response would be JSON. If the response is HTML this can be caused by a couple of different things. Oftentimes this is caused by an index.html file in the root directory of the WordPress installation. This can be resolved by either removing the index.html file or by adjusting the indexes directive on the server configuration and prioritizing index.php over index.html. Some caching plugins will also prepend HTML to the JSON response.”
I do indeed see a doc type of html.
Here’s another clue about this problem. The WooCommerce doc also states, under “Invalid Response from an AJAX Call”:
“You may also see a response of -1, This is a security failure and is caused by a cached nonce.”
Here’s what I see under the XHR tab:
Yes, I tried this. The site is loading on Google Chrome now, but the main problem persists: the credit card payment won’t go through.
I see a 404 error on Chrome console.
This doc from WooCommerce identifies several possible errors for this problem, one of them being JavaScript related. https://docs.woocommerce.com/document/endless-loadingspinner-on-the-checkout-page/
