Render Engine options greyed out?

I’m trying to tweak my render settings but, all of the sudden I am unable to select any render Engine. I’m sure there is some override setting locking it from somewhere else but I can’t find it. How do I enable render engine settings? (They are currently greyed out)
Thank You

If a rendering or Light Gen is running, these settings are greyed out. Can you check that?

There is nothing running and they are still unable to be selected or changed.

What happens if you restart Revit?
These settings are locked only if there’s a rendering process going on.

That worked. Thank You Ana