Vitaros does work for some people, but it is the least effective method of administering Alprostadil, and doesn't work for many people. Caverject is the most effective Alprostadil delivery method. However, you should be trying for more erections than is safe to achieve using Caverject.
Ideally, you want to be on 5mg daily low dose tadalafil and using a pump if you can't get erections. Keep up with the 5mg daily tadalafil even if it doesn't give erections - it improves blood circulation even in the flaccid penis, but if it does enable erections, that's perfect. You may need an occasional 20mg dose to generate an erection, but if you do this, skip the next 2 day's 5mg doses to prevent overdosing on tadalafil (and it will take that long to drop back to the 5mg daily level anyway). None of the PDE5 inhibitors work for everyone, and you might need to try another one for erections, but only tadalafil is effective as a daily low dose to protect the flaccid penis too.
It's a shame some health authorities won't provide penile rehabilitation drugs/pumps. ED drug doses are not effective for penile rehabilitation.
For a pump, the guidelines I got for penile rehabilitation were to aim for 10 mins/day or 15 mins every other day. Avoid leaving it more often than every other day. Pumping it up and letting it down several times may be more effective than pumping up and holding it for the whole duration just once. Don't use constriction rings for penile rehabilitation - only use them if you are having sex, and limit them to 30 mins max. Never allow yourself to fall asleep with a constriction ring on.
If you can get a good erection with PDE5 inhibitors, this is better than using the pump because the pump only erects the visible half of the penis. A good natural or PDE5 inhibitor enhanced erection will erect the whole organ, including the half inside the body. However, both PDE5 inhibitors and pumps have a roll to play, and you can use both.