Are you missing the Upload Featured image option? Set featured image option isn’t appearing!
I visited some forums and found that a lot of people posted: WordPress admin not showing Featured Image option, Featured Image meta box not showing up, “featured image” field not showing in the admin panel, featured image option not displaying in WordPress admin area, etc.
It’s happening for two reasons, and therefore you need to see the following two types of solutions:
1. Theme Support
Either you accidentally removed theme support for post thumbnails or you forgot to add this code while developing a theme.
If you see that the featured image option isn’t appearing on block editor while writing or editing a post, add the following code to your theme’s functions.php file:
add_theme_support( 'post-thumbnails' );
2. WordPress Multisite Case
WordPress MU users: Try going into “Network Admin”, then click on settings, then enable image upload box, and save.