You sure he's a he? and how big is he?
Could be a female that is holding off because of the season?
If you want you can assist him (or her)
Pre killed rat (size has to be proportioned to snake)
Hold gently by the back of neck (but keep a firm gentle hold)
Take tongs and introduce the rats head to your snakes mouth, lift the mouth open with the rats head and keep pushing gently till it will swallow it on it's own.
If this continues though you may have a female that is going through her breeding/eating freeze on eating.
If it is for sure a male and all temps and conditions are optimal yet he is still not taking food it may be time for a trip to the vet (I know no one wants to hear that)
Best of luck!