I was crossing the Sierras on my way to Las Vegas at 15,000 feet in my DA40 NG, which has a maximum operating altitude of 16,400 feet, when Oakland Center came on and told me to climb to 17,000 feet. I responded “unable.”
After a significant pause, the controller came back and said, “I don’t know what to tell you.”
I’m pretty sure that’s not in pilot‑controller glossary. A couple minutes later he handed me off to the next controller who gave me a five‑degree turn and 16,000 feet.