The discount coupon form action and the main cart form action are blank/empty - so the forms don't submit properly.
rwd package with custom theme
checkout/cart.phtml checkout/cart/coupon.phtml
are both overridden in the custom theme, but only text has been added and buttons re-arranged, nothing more.
If I remove those from the theme, the form actions output properly and forms work, if I put back problem recurs.
I've tried disabling/clearing cache. Doesn't happen on local development environment, only happens on Cloudways server. Varnish is disabled on the server. Varnish extension is disabled as well.
Ideas welcome - thank you.