I just tested my new RTX 2080 ti via my render network and the cards won't apply the AI Denoiser to the rendered images. Also tested with LW and Octane on this machine. The same. My 1080 ti and 780 ti cards are working fine.
Windows 10, Nvidia Driver 417.35 and Octane 4.01.1.0.
Solution: uncheck "Denoise on completion"
I don't think it's intended to work that way, or is it?