A few things could be at play here. If Kuri doesn’t understand what you’ve said, or where you want him to go, he will let you know with a pulsing orange heart light and a confused sound.
If you issue a voice command while Kuri is offline, he makes a confused sound and pulses a red heart light twice.
Kuri might also shake his head no if someone else is controlling him with Override Mode. You’ll see a purple heart light if this is the case. If you’d like him to stop, just say “Hey Kuri, stop.” Then you can issue your own command.