If you used the in-game "Upload to Workshop" button on Windows, the resulting Workshop item came out empty (zero files, "Build for workshop item has no content" in the Steam log). Cause: Godot was passing forward-slash paths to Steam's UGC content scanner, which uses Win32 file APIs that can't enumerate folders given Unix-style separators on Windows. Steam silently produced an empty manifest and reported back a generic Fail.
Now fixed: paths are converted to native Windows separators before the SDK call, with an existence check that fails loudly instead of silently if anything's off.
Reported by Sellyme on launch day in the Mod Policy thread. SteamCMD uploads were never affected; this only impacted the in-game button.
— Vosk