I’m a fit 50yr old, have MS, can get hard with sildinafil, but rarely cums. Dr has done an ultrasound of the penis, and it has lower blood flow. He has recommended corewave therapy.
I have not had it so can't speak from personal experience but studies show it is 70% effective so think it is worth a shot. https://pubmed.ncbi.nlm.nih.gov/33373703/