: The internal folder structure of your ZIP file is incorrect. Specifically, the project.json file might not be directly at the root level of the archive. The Fix : Follow the "Create a New Project" method outlined in the manual section. Make sure you compress only the contents of the folder, not the folder itself. When you open the new .sb3 file with an archive tool, you should immediately see project.json and asset files, not a single folder.
Because an SB3 file is structurally identical to a ZIP archive, converting a ZIP back into an SB3 is mostly a matter of correct repackaging. Why Convert ZIP back to SB3? convert zip to sb3
Blank sprites or missing sounds. Fix: Ensure all asset references in project.json match the actual files inside the ZIP. : The internal folder structure of your ZIP
