Featured Image issue in WordPress Block Editing

I am trying to add a featured image to an existing post, by adding a Featured Image block, selecting the photo from my media library, and updating the page. When I first add the image to the block, it shows up perfectly in the block editor. But then, when I click “Update,” the block goes back to being the default gray box with the upload symbol, the image vanishes, and it does not appear on the webpage.

I’ve tried clearing my cache and deactivating potential conflicting plugins, but nothing seems to fix the issue and I don’t know what else I should be troubleshooting. Any suggestions you have would be greatly appreciated!