Endless spinning wheel at Woocommerce checkout

Solution:1

Thank you to @plushyObject for generating the spark for this one.

The issue turned out that I had a legacy static html holding page in place as the site’s homepage rather than having one set up with wordpress. Simply removing the .html page and letting wordpress’s homepage take over solves the problem.

The moral of the story create your holding page in wordpress.

Solution:2

Go to Google Developer Tools, then Go to the Network tab. Click the button and make the request and let that bad boy spin out.

You mentioned the response is returning HTML. Click on the request that goes out that appears to be taking forever (/?wc-ajax=checkout) and then click on the Preview tab to display that HTML. I bet it shows an error or a clue, anyway.