Cracks are normal. Every house will crack when it is built. If the house you buy doesn't crack, it's not normal. The main cause of cracks is the change of foundation bearing capacity, which is inevitable. A house without cracks is too rigid, and the result is that there will be great problems without warning when it is destroyed. You don't have to worry about this, as long as the joints are not too big.
If the seam is too big, you should go to your corresponding property management company, and they will adjust it for you.