Just installed new Windows version (Windows 10), along with ffmpeg as instructed. Try to "add clip" and get one of two error windows: (1) Clip is Invalid, will be removed from project. (Trying to add an MOV and MP3 or WAV file.) (2) kdenlive.exe - no disk: There is no disk in the drive. Please insert a disk into drive I:. Cancel - Try Again - Continue. Forced to close program as it is unresponsive at this point.
Can you successfully play these clips using the ffplay you installed together with Kdenlive? Apropos: Please fill in the platform correctly next time: it's "MS Windows". (And don't ask me why there's Windows CE available at all)
A reboot fixed the issue for me.