Wireless keyboard not working

You could look at this article but I'm afraid you'll still need to contact Apple Support: If you can't connect your iPad to your Magic Keyboard, Smart Keyboard, or Smart Keyboard Folio - Apple Support

The alert that you report is typically characteristic 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.