Hi,
I create a category, it is saved, but there is no category in the tab. I go to PHP. My admin find the _k2_categories table and see the created category, and the categories that were previously created. I understand it is not assigned an ID to this category. What needs to be done to assign an id to a category? Help me please.
In attach error screenshots.

If the ID is 0 it means something is broken in K2. Re-install both Joomla and K2 just to be sure.

Hi,
Thanks for such method! But I have a lot of data in K2 that Joomla itself. Since a very large portal! What other solutions are there for this problem?

Re-install Joomla using the Joomla Update component and simply install K2 (v2.9.1 [dev] from github.com/getk2/k2/archive/master.zip ) on top of what you have already. You won't lose any data.

If you wanna be sure, just take a backup of your site and database before doing the above.

Hi, Thanks for the tip.
There was a problem in the database, apparently it was not updated correctly before, the tables in the database were without the editing function. But I fixed it, and transferred it to the new Joomla and K2.

Good to know.