I’m going to move this to Beyond the Manual because staff won’t answer questions on use of non-PG materials
Tile often engraves basically invisibly - people fill the divot with markers or crayons or paint…so is it still completely smooth or is there an engraved mark that is the same colour as everything else?
Also, what are you trying to engrave onto the tile? What do you have your power/speed set to?
This thread: Etching Tile has a ridiculous amount of great info!