Hello,
Our developer wrote to me, that this issue is caused by the enabled option " Search engine friendly (SEF) URL"
in the Backend of Joomla (Version 3.9.27).This bug should be fixed by the Joomsocial Team.
Here is his detailed answer ( i translated it with google translator):
"Internally, JoomSocial uses the static method JRoute :: (), which is set to 'search engine friendly URL' in our configuration.
The links for the announcements (aka bulletins) are provided by the class
CRoute generated using the static method '' which is implemented in the file components / com_community / libraries / core.php.
In line 1407, the static method '_' of the JRoute class is used internally to generate the URL.
The input 'index.php? Option = com_community & view = groups & task = viewbulletin & groupid = 2 & bulletinid = 2 & Itemid = 136'
is used by JRoute :: _ () in
'/index.php/de/component/community/groups/viewbulletin/2-infos-zu-tag-1?groupid=2&Itemid=136'
transformed.
As a result, 'bulletinid = 2' is removed from the URL and used in
'2-info-to-day-1' converted.
However, there is no reverse conversion anywhere, so the line
1786 in the viewbulletin method in the file
components / com_community / views / groups / view.html.php
does not get a valid bulletinid and consequently an empty bulletin
loads without a valid groupid.
The invalid groupid leads to the fact that no suitable group object is loaded and thus the variable 'published' is evaluated as 'false'
which in turn triggers a redirect with the displayed error message.
The Joomsocial should test their software with the option 'Search engine friendly URL' activated. "
Kind regards