Hi everyone

I am new to the site and this is my first post. I was wondering if anyone can help. We purchased a new grey cockatiel on Monday form a local pet shop that seems to specialize in birds. It was living in a cage in the store with 2 other tiels for 2-3 weeks. The problem is I think there may be something wrong with it as it is nearly constantly just sitting on the cage floor looking out very sad like. It rarely is up on perches and I have only seen it eat once.
The pet store owner told us to keep putting our hand in to get it used to us, but it kind of backs off into a corner when we do this. I have also read on the net not to do this at first.

Just wondered as it is early days is this typical behaviour when a bird is new to a home. Will it come round? Or should I be worried is it sick or just very nervous and stressed.

Many Thanks