It's not common but I have had snakes that ONLY take frozen thawed or pre kill. I attribute it to a live rodent biting them before I acquired them. Must have been spooked. Also sometimes snakes that have been fed F/T or P/K their entire lives won't know what to do with live. But yours is too young for that to be the case I would imagine.
I'm at a loss considering the info you've given. How many meals did he/she take with the breeder before you acquired it?
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