can't import 10.6 & Big Sur

Do you mean the Media Import window does not appear when you click the Import icon or press command - I ?

If that is the case I have no idea what is causing it but as a first step you could try deleting the preferences.

Open FCP X whilst holding down the command and option keys and in the window that appears. select "Delete Preferences".

I am using FCP X 10.6 on Big Sur and my Import Window opens perfectly every time.

What exactly happens when you try to import?

Try deleting preferences.