Hi there - new puppy owner here too!
I certainly don't claim to have all the answers (sometimes none of them!) but one thing I was recommended to do - and it works with Pickle who's now 9 weeks - was to get her a
big soft floppy toy - in her case it's a huge (twice Pickle's size)soft dog - to sleep with. It gives her something to cuddle up to - and even in only a week has become her trigger for recognising it's sleep time!
We proved it works by accident when I left it out of her cage when I took her out in the car and she whined and barked incesantly, once I realised what I done, I put "big-pup" (as it has become known
) into her carry- cage and within seconds she calmed down snuggled up and went to sleep!
It's also really useful because wherever she is she seems to now know that big-pup=sleep time.
Best £2.50 I ever spent in a charity shop.
Maybe your pup is missing brothers/sisters/mum etc - Might be worth a try!