Unable to play Video

Recently for no given reason I am unable to review a video alert from either of my two outside stickup cams, when it does this the option of Share, Star or Delete is limited to just Delete and when I go to the live playback to review past events the event is not there either, this is causing me to miss motion events that I may need to see, this is probably a recent update problem again!!!! May I add this seems to be at complete random motion events because 2 minutes later the cam that has alerted me and has the problem of not being able to be viewed works perfectly and plays back the motion event.