[@mmc_jake]

What’s likely happening is that the plastic material (probably PLA) of the tile isn’t very conductive – it doesn’t let enough electricity pass through it.

When the playdough is pressed with the finger, that connects the loop of the circuit: tiny amount of electricity can go from the Makey Makey, through the wire to the alligator clip, into the tin foil, through the playdough, through the finger and then through the body back to the wrist strap and back to the Makey Makey.

When the tile is added, the path is blocked.

There are some suggestions earlier about ways to make the tile more conductive (e.g. changing the material, coating it in something).

Alternatively, you would need to look at making more of a switch that closes the loop through the mechanical action of moving/pressing the tile rather than being part of the circuit.