The TV input must be set to HDMI 1. Trying to change the channel on the TV itself will not work.
To change the channel, there is a set top box, usually located behind the TV, that must be used. There is a separate remote for the set top box labeled as such.
It can be tricky to use the remote for the set top box because many of the TVs will incorrectly respond to signals from the set top box remote. They may try to change their own channel tuner when you are trying to set the channel on the set top box.
If this happens, you will probably have to set the TV's input back to HDMI 1.
If you have the above problem when trying to control the set top box, you may need to hold the set top box remote up close to the set top box remote receiver so the TV doesn't pick up the signals. The remote receiver is a small bubble shaped device as pictured below, usually affixed to the upper left of the TV.
If you see pictures of mountains, mushrooms, or a dog, along with the message "no signal available", this is the set top box telling you there is no signal on a particular channel. Try changing the channel with the set top box remote.
If you see a "no signal available" message without the mountains, mushroom, or dog, then you probably need to set the TV input to HDMI 1.
If you see a "no signal available" message, none of the above background images, and you are certain the TV is set to HDMI 1, then the set top box is probably powered off. Use the set top box remote to turn it back on, taking care to hold the remote next to the set top box receiver so the TV does not pick up the remote signal and erroneously turn itself off.
Be patient. The set top box will take about 30 seconds to power up.