Hi James,
I have tried the steps provided by your link and it worked well.
If you are using Dynamics 365 V9.X, you should go to Custom Service Hub to add KB articles.


If you still can not add the image, please check the following points.
1.Did you successfully add the image to web resource?
If not, confirm that you have the permissions to write/edit web resources.

2.Which image file you want to add to KB articles?

We could only add .png, .jpeg, or .gif files.
3.Did the system provide any issue?
Could you kindly share more information to let us help you better.
Hope it helps.
Best Regards
Leo