A dog that is not able to stand up is an emergency, so first I'd find a new vet.
If this happens after shots it is a serious reaction that needs treatment immediately. Since the pup is still having symptoms three days late with no treatment, it may not have been the shots (but that has to be the assumption after giving any vaccine...that the problem is a reaction...). Or it could have been the shots that damaged the liver further and caused neurologic problems if the puppy has a liver shunt and brought out the symptoms.
I would get your pup bile acid tested today if possible (make sure they send it out to a lab and don't do this test in-house) and if all is fine the pup will probably need to see a neurologist.
