Why could the activation server not be reached on my iPad

My iPad Air 2 was restarted after losing battery, and I was asked to activate it. When I put the right Apple ID details in to the activation lock, it said it couldn’t be activated. I’ve tried many times and the outcome remains the same. Why do I even need to activate my iPad if there wasn’t a software update taking place? Is there a chance I have lost any data in the iPad?