This is a common issue among men which can occur at various times in life.
When Viagra and other pharmaceutical aids cease to work and everything is fine physically after a medical examination it is safe to conclude that the issue is psychological and not physical.
The mind is extremely powerful and can easily override any chemical input like Viagra.
Clients that come to hypnotherapy for relief of this problem always find a root cause or cluster of causes that have contributed to Erectile Dysfunction.
The part of the brain that creates an erection is linked to our imagination which is controlled by the subconscious, unconscious mind; it is not logical which is why it is difficult to understand when a person is perfectly fit and healthy.
An erection is created through arousal which is a feeling; feelings are controlled by the unconscious mind. We cannot consciously think ourselves to an erection we can imagine a situation where a feeling of arousal comes upon us which creates an erection.
It is the subconscious which is also the imagination that is at play not logical thought.
Morning glory is a prime example of this as the unconscious is most open at that time just before awakening.
The positive aspect of this is that the mind is creating a thought or feeling that is stopping blood flow and arousal . So as we explore that level of the mind we can find and create a solution.
I have found that it is mostly an elaborate way that the mind creates a defense mechanism, a switch that just goes into the off position.
Another tendency is that after it happens a few times a mental expectancy can be created of it not happening in the future. Using of a variety of hypnotic, therapeutic techniques positive mental expectancy can be created with resolution of the issue.