Depending on how much your feeding him, and with what frequency. Maybe he's just not hungry. Not to mention the variables of his husbandry. I guess if you explained more, it would be easier to access your situation.
She's eating a small rat every 10 days and has been a great feeder until recently. I have her in a 36x18x18 terrarium with lots of varied hiding spots and ecoearth. Temp reads between 85 and 90