Let me express the circumstance I had faced during my first El Capitan download process. After I clicked on the download button from App Store, The "busy" wheel began to spin in the upper left, and I thought to give it some time. After a while, nothing moved. The detail page of El Capitan on the App store shows greyed download button (means that downloaded), but on its left it says "there's been an error'.
My head is spinning now, please help