"Read More" Is Not Working in My Article
If you try to use this any other Menu Item such as a Single Article it will not work.
The "Read More" option is only intended for use with the Category Blog Menu Item. It works in Category Blog because this menu item is intended to display the introduction of a text whereas a Single Article Menu Item is intended to display the full article.
If "Read More" is not working in a category blog menu item, check your article options to make sure "Show Read More" is set to show. There are three places this can be changed. See How to Change Article Options in Joomla.