not compatible with WP 5.3

It was a nice plugin, but it’s not updated and broken in WordPress 5.3.
You can try to follow https://ww.wp.xz.cn/support/topic/5-3-broke-this-plugin/ to replace with “Media Library Categories” WITHOUT loosing your existing categories.

Dear developers,
Stop giving yourself 5-star-ratings (these do seem odd, right?) and start fixing your plugin please…