You may have better luck with a gel for your rooting hormone and a medium that allows more O2 to the root zone. Rockwool is a widely used, non-hydro/aero method to accomplish this, just remember to soak the cubes in 5.5ph solution for at least an hour and then vigorously shake most of the moisture out of each cube before use. Also, we've had better results when NOT inserting cuttings into the provided holes. Creating a small slit with a sanitized pointy object creates a snug fit and the manufacturers hole then provides more access for O2 to the new roots. Also, a visual window to monitor early progress.
Hope this helps!
Edit- Also, agreeing with *Buds, make sure your scissors,scalpel,etc are very sharp and sanitized.