It is probably too young.
The kids need to be able to sit independently and stably to be able to absorb the shocks and movements.

I didn't put mine in the carrier until it was 15 months old.
And in contrast to the baby carrier, it still doesn't sleep in the harness when it's almost 2 years old.
I suppose it's too uncomfortable for that...

Hi, according to the manufacturer, 9 months is the minimum age. However, we did it in such a way that our child could sit up independently and sit alone for a longer period of time.