Problem with using custom css

Hello, I am trying to implement a Custom CSS and have problems with it.

After using the command “Strg+P” and typing in “Custom CSS” I get to the side “Links” but no block for Custom CSS appears. Also, I noticed that the Power Up of Custom CSS is kinda grayed out.
I tried it on my desktop app but also in the browser. It’s the same problem.

Hope someone can help with this.
Thanks in advance!

Could you post a screenshot/GIF of what you are seeing?