If you're using Safari, try the following:
Hope this helps.
Using Safari with macOS Version 10.14.5
Click on Safari in menu bar at top of screen
Scroll to Preferences
Choose Websites at top of preferences window
On left side scroll down to Pop-up Windows, click to open
On right side is your list of Currently Open Websides and Configured Websites
For each website you can choose:
Block and Notify
Note: If you have Adope Flash Player installed it will show up usder Plug-ins on left.
If you find that your Mac slows way down and that darn beach ball spins forever...
make sure you choose Off or Ask. If you leave it On after you use it for Pogo, you will
probably have this problem that turns your Mac into a snail.
Pogo will tell you that Flash Player is not installed but when that happens just go to
your Preferences following the instructions above. Have fun playing Pogo games!