Cannot add 16×16 logo graphics

Hello,

somehow it won’t let me add a 16x16px Logo. WP is at 4.4.1 and I just installed White Label CMS. I tried gif, png and jpg formats.
I clicked on Upload inside White Label CMS setup, the pic gets uploaded and when clicking on “place in post” (using german wp, could be called differently) the filed is left blank.

greetings,
mpek

https://ww.wp.xz.cn/plugins/white-label-cms/