My chiuahau had a c section yesterday and will not nurse or lick the puppies?

my vet told me to put the pups with her evry hour (not alone but with my supervision) and my mentor told me to talk to the mother dog and rub them on her while petting her to try and coax her to lick them. I have keept them warm am feeding them every two hrs by bottle as well as burping them and stimulating them to pee and poop. They all seem to b doing well however despite my best efforts one passed away this morning. I am fully prepared to keep nurturing the pups but am wondering if there is anyone out there that has been through this and has some more ideas.Please dont leave any nasty comment as I have done every thing possible to help these guys survive,my mentor and vet are great however their advice just does not seem to be working. any positive comments to help would be welcomed.