...view the Categories tree - on side ??

By creating a category listing module as explained here:
www.hikashop.com/en/support/documentatio...ml#categories_module

Please make sure that you configure it the same way as the module on our demo website :
www.demo.hikashop.com/administrator/inde...odules&task=edit&cid []=120

What other page ?
If you don't give information on what you do, we can't help you.
Could you give a link to that page ? Could you do a screenshot of the options of your module ?

Mmm. It's still vague as we don't know what happen when you click on a link. What is the link ? What does it display ?
I would guess that it might come from the "menu" option of the module. Sometimes, depending on your joomla/server you might have to create yourself a categories/products listing menu and set it in that option once the menu works instead of using the one created automatically.

The value will only be changed on the options of the menu/module once you click on the "save" button of the menu/module options screen.

Also, it is quite rare but it can potentially come from a browser user session issue so you might want to try with another browser just to make sure that it's not that.