how can i get the checkmark back to show in the check box

1. Let's check to see which macOS you have. On your Mac, click on the Apple icon at the top left corner of the Menu Bar. Then click on About this Mac. It should tell you which macOS you are running under the Overview tab.
2. Your second point is not understood by me. Can you provide more details on which box and check mark that you are referring to?

Axel F.

wot90s wrote:

mac Pro 2020 Big Sur.

if I have a screen up to check mark and I need to fill in answers and click in the box, my check mark will no show up. So I can’t tell if it is actually checked .

Paint a bigger picture— what is it you are trying to do...(?)

Talking about check marks does not adequately describe the issue.

A 2020 Mac will not run "High Sierra"

If you are trying to trade-in for a newer purchase, the 2020's are still considered new and are not available for trade in.

Apple Trade In - Apple