The cell conversion that Stemson is doing has 3 steps:
bloods cells --> iPSCs
iPSCs --> neural crest cells
neural crest cells --> dp cells
And each step takes weeks
(not sure about how they get epithelial cells)
Also, I think they need to multiply/expand/clone the iPSCs obtained from the blood before reprograming it do become nc cells, and this would be an extra stage in between all that.
In a nutshell, they are taking your blood and reprograming it do become hair follicle cells, then they implant it in your head and new hair will grow. But as you can see there is a lot going on under the hood.
It is no surprise it is taking a considerable amount of time for them to be able to do all this consistently. They are probably having to create/adapt their own tools and equipment since all this tech is so new and cutting edge.