OpenCart categories are not showing up

Question

The categories have:

1. The "top" option marked already
2. They're assigned to a store
3. They're assigned to a manufacturer

And they're still not being shown. I don't think this is a code issue as it was working just fine with the default products/categories and I haven't touched the code yet.

I've researched a lot, but people always say that marking the "Top" option should solve the issue.

Please take a look into the below screenshots.

http://postimg.org/image/yv6p186kf/
http://postimg.org/image/wcl00jku7/
postimg.org/image/pbx07rj27

Thanks

Edit:

I'm using OpenCart v1.5.6

Edit 2:

It is a parent category. For those who are still researching this, please read my answer.

Answer 1

It seems to be an OpenCart bug.
Here is what I've done to fix the issue:

Instead of leaving the "Parent" field as blank, try to type a invalid name in the field so it will show the -- None -- option, select it and click on save. It solved the problem in my case. Please see the screen shot.

http://i.stack.imgur.com/WWPBY.png