My son trained in daytime at 2, but not until a year later at night. I know he was three, not six, but what worked for us was switching to cloth training pants (with plastic sheet under his bedsheet because they leak)...after a week he was trained at night as with the pull-up he didn't feel the wetness and it didn't bother him, but the cloth helped him feel wet and wake up. Also, we limited liquids for an hour or two before bedtime and got him to pee a few times in the last hour before bed. Good luck!