Magic keyboard saying “this accessory is not supported "
It just happens almost randomly, I tried rebooting, connecting it again, cleaning the Smart Connector, it doesn't work and I'm talking about the keyboard that floats the iPad.
See >>> If you see an ‘Accessory may not be supported’ alert - Apple Support
If you are using a Smart (folio) keyboard, the alert is typical of a faulty folio keyboard. The electrical connections that pass though the flexible fabric hinges typically fracture - this usually resulting in errors and/or the on-screen notification that you see.
The Smart folio keyboard itself is not repairable. The only remedy is replacement of the keyboard. If you are within your one-year limited warranty, you need to contact Apple Support or your retailer.