Render Engine options greyed out?

[vanderloo]

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

[Ana Lyubenova]

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

[vanderloo]

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

[Ana Lyubenova]

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

[vanderloo]

That worked. Thank You Ana