What is preventing rubrics from being edited?

Hi,
I posted a question on the forum, but received no reply, so have to repost it, sorry for trashing the forum with duplicates.
My issue is that even though I am clicking on the cells in the rubric I am unable to edit them.


Just to clarify, I go to the actual Edit Markbook page and click on the rubric icon there, but it’s not responsive. Not sure what is that I’m missing..
I believe it’s an easy fix, but I haven’t found a solution to it on the forum nor in the documentation. Played around with the option, but I am a complete beginner so it’s a bit of a challenge.
Thank you!