Unable to click “select category” after logging in the front end

Hi fellows,

I recently logged in the front end of my category to add an event.

I logged in successfully, but when I wanted to click the button of "select category", I could not.

The screenshot is attached below:

As you can see that the primary category has been disabled. When I click on i,t I get another error. The screenshot of that error is as follows:

404 – Category not found

Now this is the backend view of the category:

These are the primary categories that have been listed under secondary categories. Why is that so? Can anyone please explain why am I getting this error and why are the primary categories listed under secondary categories?

Waiting for your suggestions.

Kindest regards.