Menu Services On Demand is showing you this warning because some of the text has "fallen" off of the product you are building.
You can usually remedy this by troubleshooting..
1) Make sure you have removed all of the default text you don't need, like "Item " or "Description - 0.00". We put these here as place holders, to show you where the text will go, but you can backspace over them to delete.
2) If you have a lot of text, it really may need to be adjusted using FONT CONTROLS. Try lowering the font size on the items and/or descriptions, then UPDATE PREVIEW to see if your text starts showing again.
There is a separate article about where to find font controls here.