If it's not available on the Theme Store anymore, it is not compatible with the device or has been removed from the store (and no new downloads would be allowed at that point). All Themes purchased do not 'transfer' but they should be available on the Galaxy Theme store (tap the menu button on the left and go to PURCHASED ITEMS; select the Themes tab).
Yeah that's been fix nowOne thing notice is applying themes don't break dark mode anymore
That happened to me with a wallpaper I paid and was taken down for some reason ,never got it backIt was a free one. The guy who made it has lots of others, wonder why he pulled that one.