More than likely it's because you don't take it out of the cage enough. All hamsters require one on one time at least once a day. I would try taking it out of its cage and just holding it for about 5 minutes throughout the day. Remember that hamsters sleep during the day so I would do this early morning and leave it be until about 7 at night. Let it run around in its ball also. By doing that the hamster will realize that you won't let anything harm it. I almost killed my hamster the first day I got her...and now she trusts me more than ever because I've done what I've told you