Samsung galaxy tablet will not play movies in gallary

[hereathome]

I have an a galaxy s3 phone and when I click on the gallery all videos and pictures are displayed I can scroll through them and play both videos and show the pictures. My friend has a Samsung tablet that is very similar to the phone. I loaded videos and pictures into his gallery - the pictures are fine, but videos will not play and there is no thumbnail of them. However if you use the native video player and look at the videos the play fine. My question then is what setting am I missing so the both videos and pictures will play while looking through the gallery?

Thanks.