Can you tell me whether you moved up to Silver level from Bronze or moved down from Gold to Silver?
If you had moved up from Bronze to Silver then congrats, you have done a good job and you are really on the right path. Keep going. Contribute more and check out for the contests announced. Participate in them and earn more points along with some cash.
But, if you had moved down, then check out your contributions, some of them might have been deleted, due to duplicates or copied description.
I am sure, you are not of the second type but of the first one. I wish you all the best, to move up in the ladder and reach Platinum level fast.