Chances are the receiver has failed.

The Tamiya ESC doesn't regulate the voltage from the 7.2v battery down to the 6.v that the RX and servo like to run at.

The RX that usually comes with the 2PL doesn't have a B.E.C built in like some of the earlier larger RX's that came with some earlier Futaba models. So if you plug it in (even all wired up correctly) you will blow the RX.

If you brought the radio as a package from a shop they should have known this and sold you one that was compatible with your ESC.

If this is the case take it back and explain this to them and they should fit it.