What kicad version?What is your operating system?
Have you tried to create a new project? (Maybe your current project is corrupted)
"main2" is not a valid KiCad file. Where did you get it?
Is this my client's file.This is a mistake, I know what the reason is.I do not know if there are any rules that violate the community.any questions please inform me the first time.
You seem to have got gerber files there, KiCAD will only open it's own kicad_pro files..You can use the GerbView application coming with KiCAD to check his files..