RooTooth don't connect to Roomba

I have just purchased 3 RooTooth to communicate with the roomba. An I am trying to communicate with the roomba with no success.

I can communicate with the virtual comm port with the rootooth to enter de command mode sending de $$$ world and de — to exit with success, but if i send any order to the roomba has no effect.

I have much older rootooth and erery works fine with it. any suggestion about what can happends

thanks