Snake oil. I can't find any claims that it is effective for men with ED or atrophy as a result of prostate cancer treatments; the men that it seems to be targeting are those with psychological ED rather than mechanical ED.
To get an erection, the brain tells the blood to flood to the penis and pubis, and then closes off the exit gates so that the blood is held there (like an imaginary tourniquet). PCa-induced ED is down to the inability of the nerve bundles to send the necessary messages to the brain, and atrophy is due to the death of the spongy tissue of the cavernous nervosa that would normally expand to hold the blood. I can't see any physiological explanation or how injecting plasma to the area could possibly:
a) rejuvenate dead cells
b) send helpful messages to the brain, or
c) create the tourniquet that would hold blood where it is needed, in the penis and around the pubis
For a man with emotional problems, performance anxiety, depression I can see that injecting plasma may give him enough of a confidence boost to perhaps get and sustain an erection where he would normally be unable to - but if it is a psychological response, I guess you could inject Ribena with the same result?
"Life can only be understood backwards; but it must be lived forwards." Soren Kierkegaard