Can money buy happiness? Yes.
Can money buy all happinesses? Well, that would depend if things such as true love make you happy, but for the common person, no.
Money can buy the means to happiness, but what would really determine the happiness is your experience with what you have. For example: If you buy a video game, and you enjoyed it, then the money bought you something which gave you happiness, therefore, money essentially bought you happiness. The only merit to the saying is that money can't buy all things that make you happy.