Thumbnails not showing

Hi together,

I want to make use of image thumbnails. I´ve predefined some, but I am not able to get it to work. If I generate the thumbnail, the result will be sth. like this:

string(197) "<img width="80" height="80" alt="" src="[/cover/image-thumb__413__tooltip/H52007.jpeg](http://domain/cover/image-thumb__413__tooltip/H52007.jpeg)" srcset="[/cover/image-thumb__413__tooltip/H52007.jpeg 1x](http://domain/cover/image-thumb__413__tooltip/H52007.jpeg),[ /cover/image-thumb__413__tooltip/H52007@2x.jpeg 2x](http://domain/cover/image-thumb__413__tooltip/H52007@2x.jpeg)" />"

But if I call the URL (/cover/image-thumb__413__tooltip/H52007.jpeg) directly, I get the following error:

The controller must return a “Symfony\Component\HttpFoundation\Response” object but it returned null. Did you forget to add a return statement somewhere in your controller?

What am I missing?

Kind regards

Does anybody have an idea? Even if´s not the solution, it might help to get pushed in a direction.

I have observed, that the folders get created (e.g. var/tmp/image-thumbnails/cover/image-thumb__408__carousel), but there is no image in it. Imagick is installed. I do not get any errors. Any idea?

Let me add a screenshot of the requirements check for more information. It states that the webp module is missing, but it is declared as optional. Can this be the cause?

add |raw to your twig thing when generating the thumbnail