Featured Image issue

When editing individual location pages, I am having an issue adding a featured image. I can add a “Post Featured Image” Gutenberg block and upload an image successfully, and the image shows up in the editor page. But when I “Update” the page, the image vanishes, the “Post Featured Image” block goes back to its original gray box, and there is no image shown on the location page.

This isn’t a problem with images in general; I can add an “Image” block on a location page (see https://edna.meghanmshea.su.domains/oum-location/heal-the-bay-mpa-watch-edna-monitoring-program-2/) totally fine, just not a “Post Featured Image.” It isn’t a problem with the image itself (I’ve tried with several), or another plugin (I’ve deactivated and tested them all sequentially, and have deactivated them all at once). And it isn’t a site-wide problem. I can successfully add a “Post Featured Image” block to a generic new post, just not an OUM Location post.

Any advice you have would be greatly appreciated!