What is wrong with Jonas in The Giver?

This depends a bunch on what part of the book you are
talking about.

At the very start of the book, what is wrong
with Jonas is that he is afraid.  Or at least he is apprehensive.  He is worried about
what job he will be selected for when he becomes a
Twelve.

Later on in the book, what's wrong with him is that
he doesn't fit in so well anymore because he understands things his friends don't, like
how horrible war is.

Finally, after he sees the video of
his dad releasing the baby, what's wrong with them is that he thinks his society is evil
and he wants to get away from it.