I don't know why that happens, but sometimes when I want to take a screenshot the system becomes unresponsive if selecting an area. I have two monitors and a fresh installation. As you can see, the selector degraded to just being a thick circle:
I would try a different screen capture application, like Shutter, which is in the Store I believe. One other thing to ask, are you using the default login? This is usually set to Wayland. When you login, when you choose your user, don't enter the password, a cog should appear lower right - click on it and select Zorin on xorg - see if you still have the same issue.