Daytime pottying is a SEPARATE thing from night-time dryness, or nap time dryness.
Night time dryness... is not even attained until even 7 years old. This is normal and per Pediatricians.
It has to do with the child's biological development/bladder maturity/nerve connections/brain connections.
Kids... WILL have accidents at night. That is childhood. It happens. Unconsciously. They cannot always control it.
I had accidents too as a child.
My daughter is 7... and every once in awhile, she will have an accident. no biggie. I use waterproof bed pads DIRECTLY under her.
She was 5, when she then used underwear at night. Before that it was night time diapers. Normal.
My son recently made 4, and he still wears night time diapers for naps and bedtime. Normal.
If you expect NO accidents at night, at all... then that will not happen. Because, a child will have accidents. They are not perfect. And some kids sleep very deeply and don't realize it.
My daughter even had a dream once, that she WAS on the toilet... until she felt herself wet. We laughed about it, I changed the bed pad, she changed her pj's and she went back to bed. No biggie.
Punishments/scolding/rewards and waking them at night just to pee... does not help. It just creates more stress... for something they or their body cannot yet control. Perfectly.
Pull-ups at night, is useless. Because it does not hold much and it leaks. Thus, use a night-time diaper at night.
all the best,
Susan