I’d get in touch with support.dxo.com, describe your issue and ask for a fix. DxO should support you as a paying customer - and if there is a issue with 6.9, DxO should know about it.
Make sure you add good detail about what you do and expect vs. what you get. Add info about your gear, e.g. your GPU and other hardware.
Just tested this with DPL 6.9 on macOS and found that denoising worked as expected.