Solved Category List Empty after Migrating from 5.2.6

Tried it, still nothing. I also just realised that the menu tabs are not displaying either. I can see a thin bar across the top of the page with a Log in icon at the far right of the screen but no menu tabs.
 

I have fixed my menu tabs, still no categories showing though..

The error is already fixed, but this only has an effect during the migration, so it does not help, if you install Kunena again over an already migrated forum.
If you want to be sure, create a complete backup first. My suggestion if you have a backup from the old kunena tables:

1. Backup in /media/kunena the folders avatars and attachments and whatever else you need (like own ranks etc...).
2. Hint: This step is very important! If you remove Kunena not completely, it breaks the backend.
Go in the backend to Kunena -> Tools and uninstall Kunena (this step removes Kunena complete along with the database tables). 
3. Import the old Kunena tables and install Kunena 6.0 Beta 5 (it starts the Kunena migration).
4. Then import the avatars and attachments from your backup into media/kunena

It will fix also this problem:  www.kunena.org/forum/k-6-0-support/16341...ategory-button-error

Thank you. I will give that a try.