Tv audio - no sound

Use the remote to look through the TV's settings, and find the section that deals with 'Audio' in the menu.

many TV's have a setting to turn off the 'built-in' speakers, so they won't compete with an external audio setup.

Id this setting was accidentally changed, then no sound will play from the TV speakers.

or

look for a place to plug in headphones - if there are some plugged in, remove them to allow sound signal to play over the built-in speakers.

or

If the TV is connected to another device with HDMI, it's possible that the TV has decided to use that devie to play audio. Try unplugging the HDMI cables to see if sound returns.

or

Has the audio been directed to play over an external bluetooth device?

(assumption is that the volume is turned up to a reasonable level - you might turn it down to a decent level before testing further)