I've been trying for several hours to download a map for south atlantic US. What's the trick?

There's no trick but you have to be a little streetwise on these parts of internet.
Use an ad blocker to block ads and pop-ups and be careful which what you are clicking. Often the biggest and most colorful button is not what you want.

See this: Hosting site secrets

Thank you for the help. Still having trouble though. There are 2 files listed for my download. At the end of the line description for each is a download button. When I click, I get http://relink.to/frame.php?cid=b501781fa48d0cb37219a26edf025c&lid=218071508
This opens a window with a bunch of circles. The only other option that I can see is to use jdownloader which I did not want to do, but did anyway after trying everything else. After it downloads 400M of the 430M I get an error 275 reconnect blah blah blah. I have installed 2 adblockers and still no joy.

One of the circles is an open/broken one. Click on that and you will move on to the next page. Scroll down and click on 'free download', a timer will start and the end you can start the download. Close any pop-ups or extra tabs that may open.

Hi,
After clicking on the right circle, I am redirected on this link : http://relink.to/getfile.php
and there is not the button to download.
It's the same for all the maps I want to download.
Does anyone have a solution?

FileFactory's servers have been busy for the last couple of days but there are more links to try here