On my wife's computer, in the home tab, the "Cell Styles" selection is always expanded and is embedded in the ribbon with a scroll bar at the right, rather than a drop-down selection. She says it has not been this way until today and changed nothing she knows of. And indeed on my computer it is a drop-down selection just like "conditional formatting" and "format as table" next to it.

I can't find an option selection to change it. I tried running office diagnostics and also "repair" install of office. Nothing found nothing changed.

How do I get the layout back to normal (and avoid having the problem return)?