he was on his team’s half of the pitch when the ball was played up to him.

You can’t be offside in your own half.

If the rule is the same as in youth soccer, it’s not offside if you’re in your own half

I was confused about this too, but I think that you can’t be called offside if you’re on your team’s half of the pitch.

You can’t be offside if you are inside your own half when the ball is played.