Why don't these dogs eat?

I am doggy sitting for friends two dog, a black lab and multipoo. My friend does a special routine to feed them. He gets their food bowls, put them in front of them, wait for the to sit, raises his arm and slaps his legs as the signal for them to go ahead and eat. I have seen him do it and it work fine.

However it doesn’t work when I do it. They just sit there and refuse to eat. I’m think they’re not getting the message that it’s okay for them to eat. If I if put the food in my hand, the lab would eat it out of it (not so for the Multipoo).

What can I do to get them to eat.

PS They’re eating later than they normally would. Also, they haven’t been showing any other usually behavior so I don’t think they’re sick.

What can I do to get them to eat?!