Hello Burt Budensky, If the necessary codecs for MP4 playback are missing, both players may encounter issues. So, you may download the missing codecs: https://www.videoconverterfactory.com/tips/mp4-file-not-playing.html Note: Since the websites are not hosted by Microsoft, the links may change without notice. Microsoft does not guarantee the accuracy of this information.
You may also consider using alternative media players like VLC that are known for their extensive codec support. Reference: Windows Media Codecs
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