Pop up preview window

when i press the two windows next to the word preview to view my project in a new window the project is not displayed. when i close the new window and press the word preview it gives me a blank page nothing is displayed. everything is displayed when i log back in to work on the project or refresh the page but still will not display when i hit the button with the two windows. window comes up but nothing in them. FYI chome has updated 3 times since i last worked my project. don’t know if that has anything to do with it probably not just a thought

This is a known bug. If the preview disappears just type something into the editor (such as a space) and the preview will refresh.