If you are brushing through your sets during or after application and the fans ping off then we are obviously having some issue with attachment (this is soul crushing). The most likely culprit here is that your adhesive is curing before it reaches the natural lash. This is most likely due to your humidity or not working fast enough. You can try picking up slightly more adhesive or using a dehumidifier.
It could also be that there is some kind of barrier on the lashes that is preventing attachment. Perhaps the lashes are very oily and not cleansed sufficiently or the cleanser itself may not have been removed properly.