Yay! It works! Thanks for intervening.
I’ve been bashing my head against this issue for months now. I finally trial-and-errored it until I got it to work. It seems another plugin, Easy Forms for Mailchimp, was interfering with YARPP’s ability to save settings. I’m not sure why, and I don’t really want to dig into it any more than I have.
Anyway, I love the plugin and wanted to share my experience.