Problems getting new nonce for Ajax requests

I’m experiencing maddening problems in getting WordPress to generate a new nonce for subsequent Ajax requests to process a specific action. I’ve tried setting the nonce_life to something reasonably short, but that has caused other problems. I’ve tried creating a new nonce for the callback function with a unique timestamp or something similar, but then the value of the nonce can’t be compared against its name in the subsequent request.

At this stage I don’t know what to do. None of the suggestions I’ve read elsewhere from other folks are working– implementing those suggestions results in WordPress continuing to spit out a nonce that was the same as before.

I’ve referenced:

1) https://www.techytalk.info/securing-your-wordpress-plugin-ajax-calls-using-nonces/

2) https://www.garyc40.com/2010/03/5-tips-for-using-ajax-in-wordpress/

3) https://wp.tutsplus.com/tutorials/creative-coding/capabilities-and-nonces/

4) https://wordpress.stackexchange.com/questions/14751/ajax-why-multiple-calls-to-wp-create-nonce-return-same-value