Basically, if Divinity isn't properly installed, there won't be a path in the registry and the game path won't be automatically detected on launch. This means the app will never try to retrieve the latest script extender release link. If you then set the paths manually, it doesn't automatically try to get the release link again, it'll leave the link blank and thus when you try to download&install the script extender, it will throw an ArgumentException. You have to either simply restart or hit the refresh button manually to fix it.
Basically, if Divinity isn't properly installed, there won't be a path in the registry and the game path won't be automatically detected on launch. This means the app will never try to retrieve the latest script extender release link. If you then set the paths manually, it doesn't automatically try to get the release link again, it'll leave the link blank and thus when you try to download&install the script extender, it will throw an ArgumentException. You have to either simply restart or hit the refresh button manually to fix it.