AppStore will not update / and after trashing the old app, will not install the updated one

I have authorized my new Macbook Pro using iTunes, but when I go to the App Store, it does not successfully update the earlier apps that I have installed. So I deleted 2 apps and tried to install them afresh from App Store, but it gives me the following error: "We could not complete your request. Please try again later. (100)" - The failed updates also gave me the same error message except the number in parenthesis was (13). I have had this problem for over a month, so this is clearly not a server down time kind of issue. Appreciate any assistance on this. Thanks.