Tag archive doesn't work

I have several pages in my navigation that are compiled from blog posts. Two from categories and two of tags.

Suddenly one of the tag archives goes to 404.

When I go to /tag/how-to/, it works fine. When I go to /tag/events/, it goes to 404.

There are posts tagged “events.” It’s listed in the tag listing. Everything is just like the “how-to” tag that works.

I’m mystified. Any ideas?

Here are the relevant URLS:
https://marketyourbookblog.com/
https://marketyourbookblog.com/tag/events/
https://marketyourbookblog.com/tag/how-to/

Thanks.