why can't my videos play?
You're going to have to provide more information. What kind of videos, were they taken with the phone, did you download them from somewhere, is it an app such as YouTube or Netflix?
my videos (i took on my phone) will not play. it says "can't play video"
Are these stored on internal or external memory? If on SD, the card may need to be reformatted, or may need replacing. If internal, there may be another approach. What make/model device are you using?