If you tried adding existing Steam Library in your Steam Client, you might be experiencing this problem – popping up error message “New Steam Library Folder must be empty”. This error is not a bug or something, this is because we’ve added incorrect hierarchy of folders for your existing steam library.
In order to fix this issue, make sure that the folders common, depotcache, downloading, shadercache, sourcemods, temp, workshop and other appmanifest files are inside the steamapps folder.
The example folder hierarchy should be:
Now you can add your steam library without problem, Go to Steam, then Settings, open the tab Downloads and click the Steam Library Folders. Now add your steam library folder, on our example its “G:/YOUR_STEAM_LIBRARY”. It should look like the screenshot below.
After that, the number of games you already installed should appear on the Steam Library Folders table.
If you still have problem getting this fixed, don’t hesitate to comment or if you have better suggestion feel free to share on this page.