Course Thumbnail

Hello,
we are a church and simply want to add some education to our website. I have followed what you said in your earlier response on how to change the thumbnail image for the course. However, I had to totally remove the image holders and the image I uploaded still is not showing. can you assist.
You can go here to change image wp-content\plugins\learnpress\assets\images\no-image.png

[email protected]

The page I need help with: [log in to see the link]