Help with the Tutorial "Make Selective Edits" in Lightroom CC 2020

Hello everyone.

I am following the Lightroom online tutorial and have started right at the very beginning "Lightroom Get Started".

At the "Make Selective Edits" section, there are several instances during the video(s) that I am struggling with as my application behaves differently compared to the tutors.

For example, for the third video (3) on this page (https://helpx.adobe.com/lightroom-cc/how-to/edit-part-photo-lightroom-cc.html?playlist=/services/playlist.helpx/products:SG_LIGHTROOM_1_1~cc/learn-path:get-started/set-header:ccx-photographer/playlist:ccl-get-started-1/en_us.json&ref=helpx.adobe.com) titled "Use the Brush tool to change part of a photo" the tutor shows the brush performing the exposure change in the brushed area instantly.

If I follow EXACTLY the same process and settings, I only see a brushed on mask in light red - quite different to hers and in order to "see" the brushed on change, I have to hit return. Which doesn't work for me!

I've seen something similar with the other video too in this section " Edit parts of a photo with Radial Gradients" so something is amiss here that I would appreciate an expert's advice on. 

Thank you very much!