Are you sure he was eating rats before? Usually breeders start on mice.

If he was eating mice and you offered a rat, and a F/T one at that, that would make a lot of sense why he refused.

Find out what he was eating and offer exactly that, to a T.

Also, don't pre-scent by putting the rodent the tank.

Defrost and warm properly, then offer on tongs. If the snake doesn't take it right away, you can leave for a few hours to see if he does.