How do I rescue a project that won't open?

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  • I had a project that my son was working on for months. It was all working fine and he was finished with it and then we were showing it to his mom and now it won't open and he is heartbroken on Christmast. It just says "Failed to open project. Check it is a valid Construct 3 single.file (.c3p) project." Not sure how to get this fixed. Is there someone that I can contact that can help me out. Unfortunately, we are not very tech savy so I don't know how to even go about fixing this problem. Any insights or ideas would be most welcomed.


  • When you see this error on the screen, press F12 and check for error messages in the Console tab. There's usually an explanation why the project can not be opened - for example a missing file etc.

    Then you can rename the project to .ZIP, extract it to an empty folder and try to fix the issue.

    Before doing anything, make a couple of backup copies of the project first!


    Also, maybe you do have automatic backups - check "Save & Backup" section in Construct 3 Settings.

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  • I don't think we have any backups. Checking.

    I did the F12 thing and got the errors "main.js:896 Error while parsing the 'sandbox' attribute: 'allow-storage-access-by-user-activation' is an invalid sandbox flag."

    And then later "Sandbox iframe unavailable, skipped logging"

    and then later: "Sandbox iframe unavailable, skipped logging"

    And then later: "[Project] Exception opening: File format is not recognized."

    I have attached some pictures of the screen to this post.

  • Just to confirm. No backup. Just the one file. Happy to share it with anyone that can open it or fix. Anyone that has any suggestions on who to contact or reach out to for help, please let me know. I'm at my wits' end.

  • "[Project] Exception opening: File format is not recognized."

    This must be the error. Have you tried changing the extension of the project file from C3P to ZIP? If ZIP archive is corrupted and you can't extract files from it, then there's probably nothing that can be done.

  • I don't really know how to do that. Happy to try though.

  • Also got a new error. Not sure why I didn't get it before. Now it says "Refused to apply inline style because it violates the following Content Security Policy directive: "default-src 'self' blob: 'unsafe-eval'". Either the 'unsafe-inline' keyword, a hash ('sha256-2EA12+9d+s6rrc0rkdIjfmjbh6p2o0ZSXs4wbZuk/tA='), or a nonce ('nonce-...') is required to enable inline execution. Note that hashes do not apply to event handlers, style attributes and javascript: navigations unless the 'unsafe-hashes' keyword is present. Note also that 'style-src' was not explicitly set, so 'default-src' is used as a fallback."

    Added screenshot below.

  • Also is there any service I can pay for to help me out on this stuff? I'm afraid I am going to screw this up and lose the project and I am willing to pay for someone to help me on this since it means so much to my kid.

  • (deleted)

  • Nevermind! There was a backup!!! On Microsoft One-Drive! I used Calvin Tham from codementors and he helped me find the back up and save Christmas. Thank you to everyone for your help! I really appreciate it!

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