You need to downgrade your ps3 to 3.55 OFW, then you can just update it to any 4.46 CFW. In order to do that, you would first need to know what model your ps3 is, that way we would know if its able to be downgraded.
Here is where you can find if your ps3 can be downgraded, and the model number is at the back of your ps3. You would need an e3 flasher or progskeet to downgrade your ps3.