Used to work. Now continuous "checking Session". Ubuntu Linux 21.10 Firefox 86.0. I wouldn't be caught dead on social media. If you need more information, jgd (at) neon-john.com.

I have always had "delete cookies on exit" set and will continue to do so and use the "manage cookies" feature to save vital cookies. You need to specify the third party cookie site that should be in the exceptions file. There is now "enable third party cookies" setting in this version of firefox.

suggestion: Instead of trying to figure out a CC input form, simply provide the user a button to create a new number for the current checkout page.