Hello,
We have a problem with discussions in groups, the discussion itself can be created,
but when you click on the answer, the message "Error - Group discussion not found".
Best regards,
Piotr

Cześć Piotr.

Thank you for contacting us.
The problem is with your Joomla! installation.
I disabled SEF URLs on your site and discussion works. Now take a closer look at discussion URL:

ROOT/index.php?option=com_community&view=groups&task=viewdiscussion&groupid=14&topicid=5&Itemid=102[/]&lang=pl

It has menu item ID 102... but you do not have such a menu item ID. Thus you need to inspect your database and check if there is everything fine.

The solution here could be creation of nem wneu item that leads to JomSocial frontpage. Then edit it in database and change it menu item ID to 102... but you need to make sure if a record with such an ID do not exist in database, in menus table.