[Plugin: Gwolle-GB] No text or image appears in posting, where the shortcode of this plugin is

Hi,

I’ve added this

[gwolle-gb]

to a post.

But whatever text or images I add before this shortcode, it don’t appear in the posting itself! Just: nothing but the guestbook!

I’d like to add some text and an image before the guestbook text – but no chance: only the guestbook appears!

https://www.ads-software.com/extend/plugins/gwolle-gb/