Under medication for enlarged prostate and had undergone vasectomy 29 years ago. are these the reasons for not having erectile properly?

Generally no: Vasectomy should have no impact. Most drugs for enlarged prostate would also be ok, although there definitely can be issues after prostate surgery.

ED: It is unlikely that either BPH or prior vasectomy have contributed to your erectile dysfunction. The medications used for BPH (alpha blockers and 5-alpha reductase inhibitors) rarely cause any significant erection issues although they may cause ejaculation issues.

Yes: I see you are on finasteride.Erectile dysfunction is one of its side effects. The vasectomy is unrelated.