Early in The Veldt, what evidence are we given that the Happylife Home system has not made either of the adults particularly happy? What message...

Both parents show fear of the lions on the viewscreens in the nursery early on in the story. Soon afterwards, Lydia says to George:

I feel like I don't belong here. ... Can I compete with an African veldt? Can I give a bath and scrub the children as efficiently or quickly as the automatic scrub bath can? I cannot. And it isn't just me. It's you. You've been awfully nervous lately.

While they bought the Happylife home so that it would do all the work for them, the parents realize after the fact that the home has taken over parenting their children. Their children are turning on the parents, favoring the nursery. George and Lydia's dream house has become a nightmare that is tearing the family apart and ruining their children. Both parents have become increasingly uneasy and uncertain what to do. 

Bradbury's message is that technology in modern society is out of control, displacing and destroying traditional human relationships. Too much technology becomes a trap that robs people of meaning and humanity.