j7653 is absolutely right. Before you decide to start any treatment, your husband should consult a doctor (urologist) and go through a series of tests to determine the exact cause of this problem.
There are so many reasons for loss of hardness in erections. You didnt mention his age, health, your relationship, troubles, etc... Rather than even try to list them all here, it seems you need to speak with a Dr. and have the full check up.