I saw in my Web hosting logs that someone visited this site and spent a significant amount of time using the site search and guessing URLs in an unsuccessful attempt to discover the RSS feed URL - which was linked on every single page, but at the time only via an icon which I guess they didn't recognize. So I edited the Web design to label it more clearly with words as well as the icon... and in so doing I found that in fact the RSS URL (actually Atom, but they're basically compatible) was wrong, pointing at Shopify's generic Web server instead of my store's.
So, I have fixed that. I don't know how long it was broken, but I know it was not always broken because people have subscribed successfully in the past. I'm not sure what changed to break it. The correct feed URL, which is now linked on every page, is
https://files.northcoastsynthesis.com/rss/ , and I hope many of you will subscribe. (EDITED December 2019 to reflect the current URL, though the old one still works as a redirect.)