I wish you’d said how old he was because if he’s an older man, that could be part of the problem. But a man of any age can develop problems of the type you describe. There’s usually a trigger and then that first problematic experience becomes the ultimate source of the overall problem. The trigger could be anything that causes him to lose his concentration, like a bad day at the office. So there he is all aroused, and he thinks some negative thought, and there goes his sexual arousal. Now if he could completely forget about this incident, there would be no further repercussions. But if the next time he has sex he remembers the failure he encountered the last time, then worrying that it might happen again can cause him to fail again. And then it can become a vicious cycle. And if he’s having problems in bed, he’s going to start avoiding sexual encounters, as you say he’s been doing. Breaking such a cycle can be difficult. I always suggest that a man, or woman, use fantasy in order to keep them focused on something sexual in nature and keep away any thoughts of potential failure. If you get him to try that and it doesn’t work, then he may have to see a sex therapist.