Starting from version 4.0 DXMAPS make use of vectorial maps and the programming library used requires that your graphic card and browser supports WebGL. Almost all modern devices and browsers support WebGL, but if you have ended up in this page is possibly because you can't see the maps but only a gray background, so continue reading.
You can determine if your system supports WebGL at https://browserleaks.com/webgl (read the WebGL Support Detection section there) and at https://get.webgl.org/
Even if your browser supports WebGL, it could happen that you have to enable it in its configuration options. See https://superuser.com/questions/836832/how-can-i-enable-webgl-in-my-browser for information on how to do it in most common browsers.
Some users have reported that they fixed the issue updating the drivers of the graphic card.
You should also try using a different browser. If it works with a browser but not with another in the same computer, then it is likely that the issue is caused by some configuration option of the browser.
Unfortunately there is no way to bypass this requirement, so if your system doesn't support WebGL even after enabling it with the above information your only option is to make use of the very old version 2.8 of DXMAPS that is much more limited but that is still temporally available.