Solved Succecfully installed but NO kunena at components

Hello!
I installed joomla 4.1. All worked fine. I installed Admin tools, also successfully. 
Then I installed Kunena. As you see it is in the extensions. But I don't see Kunena dashboard.
What is wrong? During installation I got "Package successfully installed" massage  and "Error 404"
And my Joomla dashboard become strange and as you see the words: undefined constant "Kunena\Forum\Libraries\Factory\KPATH_ADMIN"
You can see the images in the attachment.
 

I uninstalled Kunena. How can I install it without problems in my Joomla 4?
 

I don't know if your admin tools specially set it up and if that affected kuena.
And how you removed kunena again normally this has to be done via Kunena Forum: Tools
so if you have removed it via joomla management there may be something more happening in the database.
but normal if your hoster have  the right requirements could it just be installed as described here
www.kunena.org/docs/en/basics/installation/installation-k6-0

I reinstalled Kunena and now it shows this (screenshot in the attachment  )
 

I reinstalled it via Extensions manager and then due to error in my Joomla Dashboard ("Kunena\Forum\Libraries\Factory\KPATH_ADMIN") I deleted all files of kunena in my Core File Manager.

it looks a bit like this error message
www.kunena.org/forum/installation-issues...-installation#223100
only his solution may not be entirely suitable for your site.
For example, if you have a backup from before you installed kunena I would put it back and try again.
And if you've just started everything do it all over again start with everything (including an empty database)

I had active forum with big database. My site is not new. And I have backup only from the time when I had Joomla 3.10 before upgrading to Joomla 4.
So now my joomla works great. I installed several extensions already. But problem with kunena.

Which Kunena version contain the backup of Joomla 3.10? The upgrade works only from K5.1 or K5.2.
Create a test installation with your Joomla 3.10 backup and follow this guide: docs.kunena.org/en/basics/upgrade/upgrade-k6-0

Thank you Rich!
I forgot to see which Kunena version was before upgrade.
I have backup of my Kunena forum. How can I see it version?

Hello,
if you have an Akeeba backup of the old site maybe running it locally with xampp or wamp on your computer/laptop