I removed the image you included. It had a lot of personal and license information in it.
Don’t worry, I was able to find your licenses!
Four years ago you requested a downgrade from 2021 to 2020. I can’t get through to the notes to find out why you needed to be using 2020 and not 2021. It may be that you are trying a combination of the 2020 serial number and the 2021 authorization code. I will send the right values to you in a message.
I did test adding your license and removing it, and the activation did work.