There are a couple of reasons why you might not be able to open pictures or videos you receive to view them in full-size or save them:
- your friend's connection wasn't strong enough when uploading the picture or video, and so the picture or video didn't send properly
- your friend's phone didn't completely finish uploading the picture or video
Here's a couple of things you can try:
- open the picture or video again later
- ask your friend to resend the picture or video