Check your Explore tool settings:
How is yours set? If you zoom in much closer, or use ctrl+drag a box with the Explore tool are you able to get the pop-up to appear?
I have this problem also. I am using pro 2.42 . I have also experienced this on earlier versions. After working in a project for a while, pop-ups and graphic selection from the map will quit working. This affects my desktop, laptop computers and the computers at my client sites as well. Saving, quitting, and re-opening the project seems to fix the problem. But this is not desirable behavior.
PS: This problem seems to be caused by a hang-up with selection. Since posting this, I've noticed that when I have the forever-wait for pop-ups and graphical selections, it is associated with a cycling of the blue "Selecting" indicator at the bottom right corner of the map. I can make this stop by selecting something form a table, but when I go back to selecting or invoking a pop-up form the map, it goes back into its forever cycle again until I quit and restart. This behavior may be related to having done things with geoprocessing models -- which is one difference between the before and after restart conditions.