We are using magento 1.9
When you click on the Manage Category, for some reason i couldnt expand the main category.
I cant even click the main category. Add Sub Categories / Root category is also not working.
Meanwhile when adding a product works well.
Can anyone help me resolve this issue?
First of all I think you are being a little off topic - this board is for hosting and performance discussion.
Did your problem started out of blue. From my personal experience those types of issues happen after you install new plugin or perform an upgrade.