Apologies for being late to this conversation, I don't drop in so often now. I am an Invercorp user and have also experienced the failure to have any effect. Disappointing to say the least when it happens.
Then I tried using the pump before injecting. I reasoned that if the cavernosum (sp) is deflated it was a small target and easily missed. Since switching to this method I have not had a single failure.
The usual caveats, we are all different. I had a prostatectomy and Radiotherapy and have no 'natural ability' to generate an erection.
Cheers all, I hope that you have equal success. Invercorp is an amazing product (when it works) that doesn't seem to have any downside to it