Got the same issue, but i’m using UE4.27
Tried everything, reinstalling the plugin and trying to enable it everywhere.
The plugin is 100% installed because I can see it in the Engine Plugin folder, but I can’t find it or enable it in my project or through the vault.
Also checked if its the most up to date version of epic launcher and quixel bridge and the plugin itself.
My kind developer collegue solved it by copy pasting the plugin from the engine files into a plugin folder of the project where you wish to use it
so copy → Engine > Plugins > MegascansPlugin
paste → “your unreal project” > create Plugins folder if not already there and paste the MegascansPlugin