cell colour does not change

Hi Folks,
I do not know how I have confused myself.
All I want to is to colour certain cells. Yellow, pink, red or whatever.
Let us say I am on C7. I try the background colour icon and that will only work if I then click the input line. When I go out of C7 it immediately goes back to no fill.
If I go through format cells it doesn’t work at all. It does not even show a new colour as shown.
Even when I open older spreadsheets the colour has disappeared. It used to work.

image description

Any help will be appreciated.

Libre Office Version: 6.2.5.2

Windows 10 version 1803

Did you choose a special theme? It looks like that. Try to return to the standard theme and test. Please restart LibreOffice after a change.

Nothing changes:

Otherwise, look in the menu Tools>Options>View, there in Graphics Output. No checkmark on OpenGL! There also test the other settings. Make a note of the settings beforehand. Please restart LibreOffice after a change.

Nothing changes:

Reset your user profile. Please restart LibreOffice after a change.

I wish you success!