Solved After the installation of Kunena 6.2.1 to J4.4. no searching and expanding works

I see, but as it is shown in the image attached, this is not the case, because in category named " Diskuse členů SVJ Krškova 783 a 784 " is one Topic (it can be seen in the other image placed over the index screenshot). If this has something to do with the translation, how can I disable displaying "No topics" or fix that on the Index page?

Thanks a lot for your tips on how to fix that.
M007.file

Go to Kunena -> Tools in the backend and make the statistics count.

OK, I did. (If it was meant like Tools/Recount Kunena Statistics). Unfortunately, there is no progress.

Please note that when I checked if Kunena is working properly, there were 4 items related to topics and categories. So I clicked to Delete Items next to each of them. On attempt to display Recent Topics, there are now 0 topics (as they were deleted). But when I hit "New Topic". the error 403 Forbidden error appears although I am a member of the Access Level as advised in Kunena. Would it be better to use Joomla Groups instead of Access Levels, so manually created people can use the board, including creating their own topics?

Thanks,
M007.file

But when I hit "New Topic". the error 403 Forbidden error appears although I am a member of the Access Level as advised in Kunena.

Either you have an error with the access levels, or again with the menu items.

Would it be better to use Joomla Groups instead of Access Levels, so manually created people can use the board, including creating their own topics?

Do you also need different user groups for the users you have created? docs.kunena.org/en/faq/categories-only-for-certain-user-groups

OK, I deleted Access Level, except for the Main category other already created, where was Access set to Registered and my custom-created Joomla Group. Still no luck. Can you please point me yet, where the issue might be? Still, I see there are 403 errors in an attempt to create a new topic. I really need to make it functional. If this cannot be set, I will probably start seek for some other solution, that is working.

Thanks for your assistance.

Did you clear the browser cache after making the changes?
Did you clear the cache in the Joomla sidepanel under "System" and "Maintenance"?
Do "Database" and "Global Sharing" have a green check mark?
Are all registered users activated in the Kunena Forum Dashboard under "Users"?

gindi