MOV (just like AVI) is a wrapper that contain any one of literally hundreds of video codecs in combination with any one of literally many dozens (at least) of audio codecs. So, whether a file has the MOV (or AVI) extension is not particularly important … what is very important is which codecs the MOV (or AVI) was encoded with. If a file contains codecs that are not on your computer, your computer will not be able to play the file … period.
Video formats and codecs is not a simple subject that one can just stumble through … at least not without wasting tons of time and experiencing lots of avoidable headaches. So, to get more detailed answers to solve your current issue, perhaps search these forums for words like “codecs” and “wrapper” and you will find very many posts with useful info (including many answers to this exact same question). Even better, if you plan to work with video more than once, it will serve you well going forward to do a little homework on the subject … perhaps search the web for such terms and find one of the many good resources that explain the basics of video formats and codecs. Best of luck.