For hard to root cuts I like to add a rooting hormone to the water on top of my basic recipe, which is just 1/4 strength bloom solution + RO water and a live or sterile reservoir additive (hydroguard or southern AG for live res & HOCL or h2o2 for sterile. Dutch masters zone was my go-to but it’s discontinued).
For the rooting hormone I use Hormex liquid (vitamin b1 and naa) or K-L-N (iba and naa). I usually run it at a little lower dose than the bottle recommends.
Sometimes I also dip the clones in one of those 2 liquid rooting hormones and let them soak for a few minutes before putting them in the cloner. Or I let them soak in some water with fresh aloe.
Make sure you change the water frequently when using a rooting hormone (bare minimum once a week but every 3-5 days is better IMO). The clones may still take a while to root but they should root.
If they are really difficult clones to root you may be better off using rockwool or another rooting medium. Sometimes, slow rooting clones from older moms I just take a longer cutting and put it in a solo cup filled with a rooting medium (coco, or vermiculite/perlite, or even a soilless mix) so a good 3+ inches is buried in the medium.
How old is your aero cloner? Have you dealt with any pathogen issues with it?
and what are your current cloning practices? What are your water and room temps like? How often do you change the water? What type of lighting for clones?
Also, what are your moms like? Are you taking clones that have more woody stems?