Hello Jürgen,

if I remember correctly, you are using a template override to show the contacts. Whenever you update an extension (or Joomla!), always make sure the overrides are still in sync with changes that have been made in the extension (or Joomla). It just happens that I wrote an article about it: www.simplifyyourweb.com/documentation/to...f-template-overrides

You do have to copy modifications made to the component into your override. It turns out that major changes have been made to allow for high resolution images and page load improvements. Therefore you have to go through that step to ensure you get the benefits of the modifications.

Now, thumbnails are not created apparently.
You can use the advanced parameter 'show errors' to understand why. You should see error messages in the frontend.

Make sure you update your override first, this may just be the issue here.