Hello viz_ko,
It looks like you're having issues with your Mac not taking screenshots.
You want to make sure that your Mac has the keyboard preferences set to take a screenshot. Here's how:
On your Mac, choose Apple menu > System Preferences, click Keyboard, then click Shortcuts.
This article will walk you through how to take screenshots or screen recordings on a Mac running Catalina 10.15. There is a drop down menu where you can select the OS your Mac is running if it's not on the latest one.
Take screenshots or screen recordings on Mac
If you're still having the same issue after following the article you can check and see if your Mac has access to screen recording. This article will show you how:
Control access to screen recording on Mac
Hope this helps, cheers!