I wouldn't be stressing yourself out over the animal not switching.. Sounds like you have easy access to live rats and it seems to be going well. People on here will tell you that every animal can be switched to FT which I firmly disagree with but that's neither here nor there. I don't even try to switch my females to FT until they hit medium rats. Be prepared that some won't switch. Sure you can do what some suggest and starve the animal til they have no choice but that isn't my cup of tea... Point in all of this is I wouldn't stress about it. Get the husbandry on point and keep feeding the animal.