As you are on ubuntu, when you mouse is over the page in firefox, click on <CTRL>right button and select “Source code of the page”. A new page will be opened. On this page, search the string openlayers.org. Do you have ?
<script src=“https://openlayers.org/en/latest/build/ol.js” type=“text/javascript”>
<link href=“https://openlayers.org/en/latest/css/ol.css” rel=“stylesheet” type=“text/css” />
If YES, you need to do what is shown on Help with Maps in Narrative Web Site needed - #12 by DaveSch