I cannot use sidecar between mac mini M1 and iPad air 4th

astro_shishimaru,

Thanks for confirming that for us. Are both devices running the latest version of macOS and iPadOS ( macOS 11.4 and iPadOS 14.6)? Are both devices connect to the same Wi-Fi network and using the same Apple ID?

If so, you can try restarting both devices, toggle handoff and bluetooth off and on for both devices.

You can also test it in another user to confirm it is happening system wide: Set up users, guests, and groups on Mac

Restart your iPad

Log out, sleep, wake, restart, or shut down your Mac

Use Handoff to continue tasks on your other devices

Let us know!

Welcome to Apple Support Communities astro_shishimaru,

Being able to use your iPad to extend or mirror your Mac's display with Sidecar is an awesome feature to use. We'd be happy to help. Does your iPad meed the requirements needed to use SideCar? According to this article: Use your iPad as a second display for your Mac with Sidecar you need the following:

• iPad Pro: all models
• iPad (6th generation) or newer
• iPad mini (5th generation) or newer
• iPad Air (3rd generation) or newer

• Both devices must be signed in to iCloud with the same Apple ID using two-factor authentication.
• To use Sidecar wirelessly, both devices must be within 10 meters (30 feet) of each other and have Bluetooth, Wi-Fi, and Handoff turned on. Also make sure that the iPad is not sharing its cellular connection and the Mac is not sharing its Internet connection.
• To use Sidecar over USB, make sure that your iPad is set to trust your Mac.

Hope that helps!

astro_shishimaru,

Thank you for that information. Just to make sure we're on the same page, Sidecar is working when connected via lightning cable but not via Bluetooth, do we have that right? Do you have bluetooth and Wi-Fi turned on for both devices? Also, be sure that your iPad is not sharing any cellular connection as a Personal Hotspot and your Mac is also not sharing it's connection.

Share the internet connection on Mac with other network users

How to set up a Personal Hotspot on your iPhone or iPad

If you are still having trouble, you may be able to reach out to Apple Support for further assistance. Depending on your region, you may be able to reach out to them here: Get Support.

Have a good one!