Recently, I encountered once again a problem in accessing a pop-up window that supposes to be on your screen but nowhere to find. Because our office setting is you can move from one desk to another, you are free to choose where you want to sit. I had this problem in Revit 2018 and just recently when someone asked me to do some bit of work in Revit 2017, and I need to export a view, it happened again.
when you access a tool or command, you are supposed to see a dialogue box or pop-up window relating to that command, but the box/window doesn’t appear and it seems to lock your software? Believe me or not, in many cases, the dialogue box/pop-up window is open somewhere else, but it’s in the ghost screen, so it does not appear on your screen. I tried to locate it using [Ctrl]+[Alt]+[Delete] but to no avail.
To solve this problem, you only need to press [Alt] + [Spacebar] then “M” from your keyboard and followed by your arrow keys or using your mouse.
I hope this helps. Have a great day.