Trying to Disable Pop Up Blocker
If "Pop Up Blocker" is not listed in Preferences - Security - Web Content, does that mean that the Pop Up Blocker is Disabled?
iPad, 10
macOS Safari 12?
Pop-up block option is moved to Websites pane of Safari preferences.
Safari > Preferences > Websites > Pop-up windows
Website
Click inside the box next to website name and choose "Allow".
Customize settings for each website in Safari on Mac - Apple Support
See also
Change Websites preferences in Safari on Mac