You may have already seen this other thread, but if not then check it out:
In general for avocados the botanical group/“race” of the avocado makes a huge difference in ability to root cuttings. Hass (and Hass seedlings) are dominated by the Guatemalan group genetics, which are usually very hard to get to form roots. The hardiest botanical group – the Mexican group – is also the one that happens to root most easily. Even still, it takes a lot of patience and success rates are often not good.