Problems connecting 4U and 4U+

Hello all. I just purchased a 4U+. I have read on TamaTalk that it is supposed to be able to connect to my 4U but I can't seem to get it to work. I have read multiple threads on here; I know to use second icon, second option, and then there are four ways of connecting from this screen: greeting, exchange, picture and marry. I think there's also a way you're supposed to be able to play a connection mini game. None of them work at all. Most of the time the 4U displays a blue fail sign when I do the NFC bump, but sometimes it's the 4U+. Never both though which I find odd as usually failed connections are indicated on both Tamagotchis. Any help you can provide would be much appreciated; I want to be able to unlock the new 4U+ characters!