I can't prove it, but I swear that Apple is having issues with their servers. I've personally had issues this month and I have seen an increase in these kinds of problems on here.
Try this:
download the IPSW file for your ipad. I don't want to link to the sites from here, but Google "ipad IPSW" and you'll find them.
Put your iPad in DFU mode. Not recovery mode. Then in itunes hold shift and then click on restore. It will bring up file explorer and point it to the IPSW file you downloaded. See if that works.