I don't know if anyone else noticed, but Nemesis Jax Sand chromaa aren't available for individual IP sale in the store despite being released before wave 1.1. I would really like to get one and I'm hoping they'll be available before the sale ends.
Me to, do you know when the sale ends?
Unfortunately, there is an issue with the Nemesis Jax chromas that has caused Riot to disable them from being purchased. I don't know exactly what the issue is, but hopefully it gets fixed soon.
According to the Service Status, here's what I found addressing your problem,
Network Operations – 08/25/2016 "We have disabled Nemesis Jax Chromas due to in game issues, and are currently working on a resolution."
