Question Error message after updating to 5.1

Other joomla mod_menus seem fine in my site. I also tested a kunena menu module on a different page (e.g. blog page) and works fine as well there.

I decided a mistake with the menu.
For this, I deleted all the menu items of the Kunena type and the aliases of the items from all the site menus. Then he deleted the menu of the Kunena.
In the tools, the Kunena menu was restored.
Now the menu is working, there is no error message.

I cannot just ignore this problem.

As you suggested, tried to switch to Protostar template, but I deleted this template before, for some reason I cannot reinstall it. So I downloaded a different template, Sunny Blue Template, from joomla.com and switched to it. I still get the same error message.

Screenshot attached.

Thanks, Petrovanovich, for sharing. After you deleted all Kunena menu and menu items, where did you restore them? I do not see restore field on Kunena tool page.

backend - kunena - tools - menu manager- restore kunena menu

The only thing you need to do then, is to enable the forum menu item on your main menu.

velieb wrote: Thanks, Petrovanovich, for sharing. After you deleted all Kunena menu and menu items, where did you restore them? I do not see restore field on Kunena tool page.

I wanted to add a screenshot, but only a quick form of comments worked.