I kerp seeing this accessory not supported by this device on my iPad why

See >>> If you see an ‘Accessory may not be supported’ alert - Apple Support

Are you using an accessory keyboard - such as an Apple Smart Folio Keyboard with your iPad? This 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. 

If this is your issue, be aware that the Smart keyboard itself is not repairable. The only remedy is replacement of the keyboard.