Is your tama an adult yet? If it isn't, then the love potion won't work. And I don't know if a v2 and a v3 can fall in love w/ the love potion, but I'm guessing they can, 'cuz once I got my v2 and my v3 to fall in love w/ out it.
To get the tamas to fall in love w/ the love potion, use the love potion on a tama when it's an adult, and then connect w/ another tama.