I have a client we are about do a hardwood clean, recoat water poly using the Vibe. But she has this gray in only one area and said we have to get it right. Told him to clean and scrub where I circled for test. Any other suggestions?
That looks like wear to me. The old coating is worn through and the bare wood is exposed and it has become discolored/dirty. The ONLY thing that will restore that area is a sanding to expose new wood. Then you can recoat. A "clean" and recoat will not work here because there is no way to get good results without sanding on a floor that has that level of wear/damage.