the first thing I did was to clean the contacts - no help.
The local Apple Store replaced my Smart Keyboard with a brand new one.
I don't get the "not supported" message and more, but the connect/disconnect cycle continues, together with the "chiming" noise and the iPad heating up and the battery draining - so no better at all, and I now leave the iPad disconnected from the keyboard most of the time - it's now just a very expensive screen protecter that drains my battery. Certainly the crappiest piece of technology I have ever had.
What makes it worse is that I was told categorically on chat support that Apple had extended the warranty on the Smart Keyboard to 2 years, and mine was within this timescale. However the guy who dealt with me at the store told me he was replacing it as a "special service" - effectively a favour. In addition the new keyboard, as a replacement, only has a warranty of 3 months. I think this is deceitful, to say the least.
I have purchased Apple products since the first iPod model, but this experience together with the pricing of iPhone x has Brough me to the point of researching alternatives for my laptop, phone and iPad. Well done Apple.