Can't install the software because it is not currently available from the software update server - iPad
Just solved this issue. I was using a thunderbolt hub, and connected to that was:


My iPhone
Power Supply


I removed the power supply and connected it to another thunderbolt port and it worked. In my case, I think it had something to do with the power and the iPhone being in the same hub - maybe the power adapter was pushing too much power into the hub.. god knows, but it's fixed!