sidecar imac ipad screen times out

Hello woopgaroo,

Welcome to the Apple Support Communities. It sounds like there are issues with initiating SideCar. We'll do what we can to help.

These might help:

• If you haven't already, be sure to back up then update your Mac: How to update the software on your Mac
• Check to make sure both your Mac and iPad meet the requirements: Use your iPad as a second display for your Mac with Sidecar
• Restart both the iPad and the Mac:
  • Restart your iPad
  • From the Apple () menu then 'Restart...'
• Turn Handoff off then back on for both devices: Use Handoff to continue a task on your other devices
• Turn Bluetooth off and then back on with both device
  • Use Bluetooth devices with Mac
  • Set up and listen to Bluetooth devices on iPad
• Set up a new user account on the Mac to see if the same thing happens: Set up users, guests, and groups on Mac

Thanks, and enjoy your day!