I've been having problems with both of my iPads (air and mini) lately with getting told that there is no connection with my server. I've Goggled the problem and done everything I was told to do, but it was getting more frequent.
Yesterday I decided to stop my power extension and unbelievably the problem stopped and hasn't returned. It shouldn't have helped by doing this, so why has it?
I had the same problem after an update (not the last one). Went into the Apple shop and they reset the connection settings. You do not lose any data just the wifi passwords and any passwords you have set for accessing sites.
Settings - General - Reset - Reset Network Settings