Error Message "Content area not found in your page"

I have just started working with Elementor. Did some home page design a few weeks ago and am just coming back to my site now to do some further work. I tried to edit a different page in Elementor but it would not load and I got an error message that says:

“Sorry the content area was not found in your page. You must call the_content function in the current template in order for Elementor to work on this page.:

I tried to enable safe mode as per the pop up prompt but Elementor still will not load. I have clicked on the various help links but honestly most of them I cannot understand the troubleshooting suggestions. I have done the ones I understand, such as deactivating plugins etc. However, many I do not understand what it means, such as “On some servers, you will have to change the SubstituteMaxLineLength.” Sorry, NO idea what that’s about!

I did follow this suggestion to try a different theme:
“Have you or the theme’s developer created a custom WordPress page template for your theme that does not include the_content function? You will need to include the_content in your code to edit it with Elementor, or switch to a different theme, which often solves the problem. First, try switching to a theme like Twenty Seventeen or GeneratePress and see if your problem is solved.”

I changed to Twenty Seventeen theme and Elementor did load. So can I assume that the “the_content function” is missing somewhere in my theme (Child Theme 10)?

That suggestion goes on to say:
“If you are a web developer and are developing a theme, add the_content function into the page template’s code. This is the line you need to add: <?php the_content(); ?> If you are not familiar with where to place this code or how to add it to the page, please contact your website developer so it can be implemented properly as we cannot provide full support for that. ”

So my questions are:

1 ~ am I likely missing the_content function?
2 ~ If yes, how and where should I add it?
3 ~ If no, what else can I try to get Elementor to load?