I am not sure exactly what you mean. but here goes.
According to your message I interpret as if you are trying to lay the tiles using grout underneath as a bed adhesive? If this is the case then this is the error as you need to lay your tile on a tile adhesive mixture and once everything is set use "grout" to fill in between the tiles.
If I am off the mark with what you are doing, my apologies, otherwise I hope this helps.