You've tried everything and more than I can think of. I wonder if you are experiencing a problem connecting to WiFi systems that require you to navigate a log-in screen before you can get to the internet? This is a typical problem encountered by iPads with many hotel systems.
One way around it may be to provide your iPad's WiFi address to the hotel's main desk, so they can pre-authorize you to use the system. For this address, see Settings - General - About.