Script doesn't work and GUI doesn't load I checked the dev console and it said document.body doesn't exist.
The reason this is happening is because you have the directive // @run-at document-start The script is running when the document just begins loading, before the body is even created, so you're trying to access the document body before it even loads
To fix this, I removed the run-at directive and the GUI appears, so I suggest you should fix this issue
Script doesn't work and GUI doesn't load
I checked the dev console and it said document.body doesn't exist.
The reason this is happening is because you have the directive // @run-at document-start
The script is running when the document just begins loading, before the body is even created, so you're trying to access the document body before it even loads
To fix this, I removed the run-at directive and the GUI appears, so I suggest you should fix this issue