Please ensure that you have the Product Type set properly.
If it is a simple product i.e. a product without any variations such as different colours etc then it should be set to “Simple Product” and the price box will appear.
If it is a variable product i.e. a product with variations such as different colours etc then it should be set to “Variable Product” and you should follow our variations guidance.
Another issue for this is managing your stock and not entering a stock level.