Featured Image not working

Hello – I recently had to reset my website back 1 week to correct a spacing error. Reset was done by Bluehost, all is working well except I cannot add a featured image to a post. The featured image shows on all past posts, but I cannot add it to a new post. The set Featured Image box does appear on the edit screen and I can choose an image and the thumbnail of the image will appear in the featured image box. But if I preview the post, the image does not appear on the post. When I return to the edit page the image is still in the set featured image box. If I save the draft of the post them thumbnail of the image is gone. I have deactivated each plug-in and no help. Thanks for any help!

https://upsideofdownsizing.com/