Read More tag not showing

Hello, the situation is:
-I have made a PAGE
-and added to it: a ROW
-to that ROW I’ve added a WIDGET from SiteOrigin: SiteOrigin Editor
-Then I adjust the editor and type in some text.
-It is my intention, to have a READ MORE TAG after a few lines, after which some more text should follow.

The END RESULT is that the page looks fine, but ALL TEXT is displayed. In other words: the READ MORE TAG does not show up.

Of course, my question is: can I fix this, and how?
Is it theme-related, or am I trying something impossible?

I have this same problem, but on the Moesia theme…any solutions figured out yet?