Cannot edit HTML in Qualtrics

I am trying to make a custom question on Qualtrics, which consists of a slider and a canvas. The canvas responds to the slider input to change some drawing settings. the user has to choose what the best settings are according to them.

I have been able to enter the JavaScript in the Qualtrics question, but I am not able to enter the HTML I require for this question.
The HTML is the following: !

I am following this tutorial (https://publicfragments.org/2015/02/06/using-the-qualtrics-javascript-api-to-create-visualizations/) , but I have not been able to save the HTML. Each time I exit the editor I see "Click to write the question text". It's not just an editor bug, as I have tried just previewing the question immediately after exiting the editor.