I am using generate press theme Catalyst. I made a Google My Maps document. I used the Own HTML code block and entered the embedded Iframe code here, but once I safe it the map takes over the header and it is shown as the top header for some reason and not just a part of the block in the text.
Strange. I did as you asked and made the page first. I wanted to check it before I closed all the plugins and it seem to work. Can it be something on the home page that is causing the error? I included the link.