stuck in update mode

brand new ipad 6th gen. setup from itunes desktop pc using backup form old ipad...worked great. few days later connected to itunes to move some more music to ipad....popup showed ios 12.1 available - selected install and now cant use the ipad. all I get is a black screen with the itunes log and cord on it. Spent 55 minutes chatting with support and they could not fix it. When I restart itunes and try agian, it goes right to 'cannot update must restore...click that option and it just hangs...HELP!

Thanks!