Microsoft Edge does not currently allow individual exceptions to be added to the pop-up blocker. As such, if you need pop ups to appear for a particular site you will need to turn off the pop up blocker for all sites. See the steps below to do so.
1. Select the button near the top-right of your Edge Window.
2. Select 'Settings' from the drop-down menu.
3. Scroll to the bottom of settings and select the 'View advanced settings' option.
4. Switch the 'Block pop-ups' option to 'Off'