How did you transfer it to your computer and how are you actually hitting play on the file? I have gotten the same result when I forgot to actually put the file on my computer and then came back a day or two later and hit play and nothing happened. It was because I was playing the file from an sd card or email or something the first time and it was fine, but then I removed the source file and when you try to play obviously you get nothing.
If you emailed it, and have since deleted the email, go back and pull the deleted email and reimport. If you used messenger, the same. If you used airdrop, check your downloads folder for the original file or maybe trash in case you have deleted your downloads recently. Or if you still have the original you can try to reimport and see if you get better results.