Section Plane Button Missing

The section plane button is missing from SU Pro 2018, but the other three buttons are visible; display section planes,display section cut, display section fill. From the Tools tab I can click and use the Section plane function though.

I just re-downloaded SU 2018 today after an OS crash/ re-install of Windows 10. Tried restarting, re-locating the tool bar horizontal and vertical, toggling the visibility of the tool bar.
Any fixes?

did you try a right click, reset to default?

or view/toolbars/section reset - which may be the same thing?

View/toolbars/section reset.Thank you!