This error keeps popping up more and more frequently for people - including myself. One thing I've noticed is that it happens more often when double-clicking the .c3p file in Windows Explorer. Instead, try launching C3, then using its Open - File menu.

i finnaly solve it. idk why when i use the version of r388.2 it work for no reason. finnaly i can sleep rn

i need help. idk why but i cant open my game project on construct 3 . when i open the file there is an error said "Failed to open project. Check it is a valid Construct 3 single-file (.c3p) project" but its litterly c3p file. last time i open that file was 1 month ago (i dint change nothin) . and idk why i cant open that file rn, i did everything that i can but still not work, pls help me i rlly need that file to work. im rlly sorry for having bad english