If the Screen Reader starts reading when you click the 'Play' button but it's unable to read the whole text and it stops suddendly, the problem could be due to some invalid characters present in the HTML of the page. If the HTML embed scripting languages, some page breaks, etc the Screen Reader could be altered and prevented to work normally.
Normally this can be solved changing the CSS selectors to match in a more specific way the text in the page to be read by the Screen Reader. Using a more specific set of CSS selectors the text in the page that is relevant for reading can be selected skipping all other elements that could cause malfuction.
As an alternative you can use play buttons directly embedded inside Joomla! contents using the handful editor button: