I had an issue, but I figured it out. The rhythm is not the same as the one on the wikipedia page - which I was already familiar with. After looking at my recordings I realized I was playing it straight, but the default knock recording has a swing/triplet feel.

straight: DAA DA-DA DA DA, DA DA

swung: DAA DA D-DA DA, DA DA

I hope my highly rigorous notation is helpful here

edit - in hindsight this has nothing to do with your problem

I couldn't get it to pass on my phone, but "scram"/"get out of here" is equivalent to a password rejected/401 response. A single knock does not match the expected pattern, so you would expect it to be rejected.