These buttons only function when html has not been applied to the text box. To find out if html has been applied:
  1. Click on the detail page to edit
  2. Click the settings gear inside the text block
  3. Click the HTML button in the top left of the style menu
  4. Search for any text that says font size = ""
If font size is present in that box, then the size of the text can only currently be adjusted by changing that number. To return to the small, medium and large buttons, remove the font size text and click update. Then click save.