If a person refuses to acknowledge that they are schizopherned, how can we help them?
First of all, if someone is not taking their medication and is actively delusional, paranoid or has other symptoms they need to be sent to the hospital. You can have your son or daughter's psychiatrist call ahead to the hospital to tell the staff the person is coming and not to release them, to admit them. If the hospital doesn't have this reinforcement, the staff may deem the patient not to be a danger to himself or someone else, and release them back into the community.
I recommend you read the book I Am Not Sick, I Dont' Need Help by Xavier Amador, PhD who has coached family members on how to talk to loved ones who lack awareness that they have schizophrenia. As you are well aware, the hardest problem is when someone with schizophrenia lacks this awareness. A great many people have this insight yet for those who don't the road to recovery is much harder.
Amador shows you how it's possible that someone can be convinced to take medication even though they don't think they're sick. So it may be worthwhile to read this book as well as take stronger measures as needed.
Family members at the local NAMI support group in your area can also give you suggestions. Call (800) 950-NAMI (6264) to get the name and number of the affiliate in your city or town that holds weekly or monthly family support meetings.
I wish you the best outcome for whatever you're going through.