Explanations for inactive interface elements

It is known that one of the biggest problems of usability in modern software interfaces are inactive elements (“gray” buttons that cannot be pressed). This is because the user has nowhere to see why this element is inactive, and what needs to be done in order for it to be activated.

I can not put pluses to the comments. How good it would be if there was a hint near the inactive buttons: your account is less than 7 days old. I would not have had to spend half an hour studying the documentation: at the first reading, I just missed the mention of 7 days.