Getting a blank screen while trying to add a popup to my WordPress website using Elementor Pro

Question

I am an .net developer and never used or worked on WordPress. I've been trying to add an popup but stuck on this screen. I am using Elementor Pro in my listing theme. The screen I am getting:

I've been trying to add an popup but stuck on this screen. I am using Elementor Pro in my listing theme. There is not option to add any widget over here.