How do I disable adblocking in safari?

I am using Version 12.1 (13607.1.40.1.5) of Safari. If I go to Safari->Preferences->Extensions is shows that I have no extensions installed. When I visit http://kmlviewer.nsspot.net , I press the "choose file" button and select a kml file. I then get the message: "Please disable the adblock for free use." If I go to Safari->Settings for This Website, "Enable Content Blockers" is unchecked, "Auto-Play" is set to "Allow all auto-play", and "Pop-Up Windows" is set to "Allow" I do not see any other settings that would further disable ad blocking. Is there anything more I can do? There are several sample kml files out there, but you can take the text from: https://gist.github.com/EricG-Personal/589b293297f42759ba32dea3df04a7b5 and create your own .kml file easily.