I know this is pretty late, but if anyone still has this issue in 2024, there is a hack-y way to get around it.

1. Hover over the Show Question Details checkbox until you see a red crossed-out circle, and right click

2. Choose Inspect on Chrome or Inspect (Q) on Firefox (other browsers may be different).

3. This will bring up the HTML element for the checkbox (it will highlight exactly what you need to look at). This will open on the right-hand side of the screen in Chrome and on the bottom of the screen in Firefox.

4. You will see code that says <input type="checkbox" id="show_question_details" disabled="'disabled'"> == $0. Double click where it says disabled="'disabled'" and delete out the only the disabled="'disabled'" portion, and then hit Enter. You can then close the HTML elements window by clicking on the X in the top right of the window (not the whole browser window).

5. You should now be able to click on the checkbox as you normally would and the question details will show. If you refresh or navigate away from the page, the HTML code will reload, so you will have to do the above steps again each time to see the question details.

No idea why Canvas has this disabled if it clearly still works fine, but hopefully this helps someone.