The E302-0001 error would point to a problem with the hardware. To resolve the error the printer would need service or replacement parts. You can try unplugging the printer from the power and then pressing the power button 10 times while the printer is unplugged. After that, you can plug the printer into a different power source and you can try turning it on.
If you continue to get the error message, the printer would need service. You can check your service options by logging into your MyCanon account or contacting support over the phone at 1-800-652-2666.
07/31/2023: New firmware updates are available.
05/31/2023: New firmware updates are available.
05/18/2023: New firmware updates are available.
04/20/2023: New firmware version 1.4.1 is available for EOS R3
03/30/2023: New firmware updates are available.
2/07/2023: New product announcements!EOS R8 EOS R50RF-S55-210mm F5-7.1 IS STMRF24-50mm F4.5-6.3 IS STMRF15-30mm F4.5-6.3 IS STM