Taskbar does not work anymore, who can

An acquaintance borrowed my laptop and now I have it again but the taskbar does not work anymore… He says he did not do anything, but before that she worked…

I can only do something about the Windows key on the keyboard…

Who can help me?

in the bar, an icon lights / flashes (see picture)

What happens if you click on the icon?

https://www.giga.de/...n-was-tun/

I just researched for you!

The Windows Defender icon lights up in the taskbar, ie: the window of the Windows Defender called up is behind the Girlfriend window.

Look what the Defender is doing.
If there's nothing exciting, close the window and start a proper reboot (in the shutdown menu, click "Restart"). - After that you will see.

Nothing happens, because it does not work… Can't click on the clock on the right or on Excel

Googled itself and it does not work

I'm sorry! On my laptop lately, the battery level indicator was no longer. I also googled, which did not help. Only when I rebooted, everything was back!

Can you switch between open programs with Alt + Tab? Then you would also have to come to the window, which is indicated by this icon.

Great, thank you… Works again * happy * was something from Microsoft?!