iPad air 2 will not upgrade iOS

iPad Air 3 will not upgrade to latest iOS , first over WiFi it would start to update and download update , then give ERRor messege that I was no longer connected to the internet and could not complete upgrade.

Tried connecting to to different laptops with USB , keep getting error 56 , tried 3 different cables, and two different USB ports on both laptops , got same error 56 over and over again with different ports and cables.