We have been hit a few times from purchasers about why something on the thing they are trying wasn’t printed when the 3D Printer got done. Many times it is words they have raised up on the surface.
If there isn’t an error in the 3D model like a gap in the skin. Then the most likely reason is you nozzle size. If what you are trying to do is print raised up lettering from the surface of your thing, and you are using a standard font then that is your problem. Fonts are problematic for 3D printers. The average font is usually only 2 to 3 pixels wide, it looks like a lot on your monitor but for the standard .4mm 3D printer nozzle, it is way too small. Every surface of what you want to print, must be at least as wide as the nozzle you are using if not wider. If it is not as wide as your nozzle the Slicer will delete it from the gcode and most likely leave holes and other mistakes in the area where the lettering was suppose to be.
So what can you do? Be mindful of the font that you use. Hand writing fonts, you can pretty much forget. Standard fonts like Times New Roman or Arial, will work if you bolden them. Recommended use bold fonts. Nearly very computer comes with Impact.ttf installed. Unless really tiny Impact will give you no problem. Another one I like is Armada Bold. If you really want a narrow line font, then make sure that you make the surface area covered fairly large. Also use a 2mm nozzle or even smaller like one of the experimental ones 1.5.
Anyways good luck and happy printing!