How do I fix "Project not opening, check if it's a valid c3p file"?

For the past few months, I have been working on a horror game, Hidden Nightmares. After the update 350, the project, after being saved and closed, breaks. Each time I try to open it, Construct displays the same message every time:

Can anybody help me with this? F12 just shows code which is all jibberish.

Try renaming the file to .zip (but make a backup copy first). Then unpack to an empty folder and try opening it in C3 as a "project folder".

Thx, but how do i mske the c3p to zip file?

Make sure you can see file extensions:

autodesk.com/support/technical/article/caas/sfdcarticles/sfdcarticles/How-to-enable-hidden-file-extensions-in-Windows.html

Then rename .c3p extension to .zip

hello again, I cannot seem to unpack the zip file after it is converted. Is there a way to fix this?

Try using 7zip. If it can't open your project, then the file must corrupted and there's probably nothing you can do to restore it.