Try using Baking Soda. It is not quite as easy to use as a powder, since it is not as fine as powder, but it has been used many times in the past with very good results.
Make sure the body is clean.
You may also want to apply the deodorant after taking a bath, then apply a light powder also. If that does not work, then try the baking soda.
Otherwise, you may want to see your family doctor.