Is semen ysis done to test if a man is impotent?

I know of a couple who haven't had for over a year. Other than that the husband is very loving and caring and it can be said with absolute certainty that he is not having an affair. He just doesn't want to have , and if he tries to, he fails to have a strong . He has been given different tests by the doctor, Blood CP, Testosterone, Random Plasma Glucose, S. Urea, S. Creatinine, USG Whole abdomen, ECG, and Semen ysis. There was another test where it tested if the blood flow in his was normal. All tests came out normal except for a little fat around his lever and expanded prostate. He tried the semen test couple of times but failed. My question is, is the semen ysis test that necessary to determine if he is impotent? I was under the impression that it was to test a man's fertility. The husband has also earlier been to a psychiatrist who had prescribed him medicines like viagraj, stelong, herbal V but nothing helped. Any suggestions?