Is this a multiple attempt? If from a young plant, it won't root very easily, if at all... After about 60 days give or take, often less, you can get a viable clone off a plant-from-seed.
When i kept it simple, i went form some failures to nearly 0. In fact, i haven't had a clone not root since i've kept it simple.
Hve all your tools ready and sanitized. a cutting board of some sort etc. good to have your hands washed too.
Take off more than you intend to use. you will cut it to size later. place it in water immediately (properly pH'd water).
Make a 45-degree cut just below the lowest node you keep. Do notmutilate the node. Don't cut into the node. You will only slow the process down.
Remove all but ~3 leaves. Clip those leaves back to 1/2 or 2/3rds or so. This helps reduce photosynthesis (good i nthis case) and loss of moisture (i don't even use a humidity dome... ever). improves airflow, which helps avoid bad microbial growth.
upto you -- gently scrap the top-most layer off stem below the lowest node (the one you are burying with a 45-degree slash underneath it) Do not damage the vascular tissue. Scrape, don't slice.It's a different angle so you only take off a tiny tiny layer.
upto you -- use some root hormone. do not pay for a brnad name. This is like generics at a phramacy. Less is more. If using powder, coat and immediately tap off before it turns to caked on mud. throw out all contaminated root hormone. do not dip into the container, that's retarded.
optional -- i like to find cloning opportunities that offer 2 nodes i can bury. they need to be close to gether. I also want 4-5 or more above ground. The larger the cutting th emore you have to be concerned it cannibalizes itself while it has no roots. Anyway, this isn't neccessary, but nodes are going to power root growth when deprived of light and moist.
bury it in the soil you use -- assuming it inst extremely "hot" andi sn't devoid of something akin to perlite. It does need nutes, but it won't be drinking much without roots. So, initial fertilization of the soil will be good for 1-2 weeks. When it dries, give pH'd only irrigation. The main key is keeping it moist. Unlike other times, i would not let the soil go dry on top.. certain not 1" deep anyway. maybe a centimeter deep.
Within 2-3 weeks it'll have a robust enough root system to transplant, if you used a solo cup or similar to start. The only benefit of that is it is much easier to water. Big pot / small plant is bad.. even worse with a clone.
After all that, i bet it was age of the donor plant... try some root hormone if that is the case.. i'd be curious. I'm going to attempt an early clone soon myself... i never had root hormone before with my initial trials and tribulations cloning.