Can Latisse stop working? I've used it 6 years in the last 8 months my lashes won't grow. Can one build up a tolerance?

Latisse results can plateau. It may be that a combination is needed. In combination with Latisse, I typically inject and apply topically PRP for a few treatments at the beginning to improve the growth rate of the lashes. Take viviscal as well. See an expert for a formal evaluation. Best, Dr. Emer

I am not aware of any mechanism by which you could become immune to Latisse however, the medication is very sensitive to heat and light.  Has it been exposed to direct sunlight? Stored in the bathroom where it might have become inactivated due to heat?  You might also check the expiration date on the bottle to be sure it is not out of date. 

In situations like this, I always strongly advise you to get a comprehensive hair exam. It's important to rule out a number if inflammatory and autoimmune conditions. Your blood tests should be evaluated too.