Use the browser dev console to inspect the output after the change. I suspect it is being displayed, but the font size is
0 and perhaps the line height too. The Gridder template is unique in this manner to achieve its layout.
You’ll need to add you own CSS to have them display properly. I suspect this CSS is in the the old theme’s custom CSS Area. Perhaps you can temporarily activate it and copy it and paste it into the current theme’s Custom CSS area.
Hope this helps!