Got it.
Mikejolley, I found your post in the WooCommerce forum that mentioned how the pages should actually be set up —?with a shortcode on each page. First I’ve noticed that mentioned anywhere. The shortcode for each page is listed on the setup page for WooCommerce.
For whatever reason, the shortcode for my checkout page was not there when I checked. I inserted it, and now everything works fine. Just wanted to post that here because as a newbie, this was not something I thought to check.
Thanks!