I am sorry to write aboit this issue but I do not find a soultion to it on my own.
According to the instructions on how to place images that are shown as thumbnails for videos into the album I did so. The thumbs are shown in the admin and in the latest view on the index but they are not shown in the album view ? I am very confused about that.
I already cleared the cache and the brwosers cache several times. No changes. I deleted the album and mad it new. No changes. Any idea someone.