Sometimes dogs can take longer than others to hold onto bladders overnight..
There' are a couple of things you can do though..
Perhaps get up during the night to allow him out for a toilet break and over the nights you can then extend the time to a later time to encourage him to wait until you allow him out..
Ellie was awful when a pup, she drank for the sake of drinking if it was their she drink the lot, so I resorted to regular small amounts of water, about 1/4 bowl at a time and then 1/2 hour or so before refilling... Over night or when you'll out Ice-cubes are very handy, as dump in bowl and it feeds a slow supply of water..
I had Ellie since 5 months old she had been put into rescue by her previous owners, with the lame excuse that as she hadn't stopped weeing over night (at 4 months old) she was incapable of learning
She spent 3 weeks in kennels before we adopted her, we've not experienced any soiling overnight but she from the first night we brought her home had the run of the house with Jones, so would wake us up if she needed out (not every night but several time a week for the first couple) as to learning no problems there.. Not only does she do the normal doggy things but has taught herself to be a diabetic hypo warning dog..
So give it time he be fine, he's still a pup