Turn the TV on and off

Turn the TV on and off

I have a Fire Stick on a dumb TV. I've managed to link my Echo Dot 3 with the Fire Stick so it can control things like play and pause and should be able to turn the TV on and off.

The problem is I can turn the TV on by voice command to the Echo Dot, but I can't turn it off the same way; it acts like executing the command but nothing happens.

Meanwhile, I can turn the TV off by voice command on the Fire Stick remote control. My goal is to be able to turn on and off the TV by voice command on the Echo Dot. What am I doing wrong?