Browsers have taken to hiding insecure content from viewers when a page is loaded that has content coming from both secure (Moodle) and insecure sources (http rather than https). Unfortunately they tend to do this without informing the user that they have done so. The issue can be resolved by unblocking the content. 

For Firefox: 

  1. Click on the padlock in the left hand side of the URL text box (see image below).
    Location of the padlock icon
  2. Click on the right arrow.
  3. Click on Disable protection for now - highlighted below.
    Location of the disable protection button

Once you have done this any content that was blocked should be made visible.

Note: Above instructions written in August 2023 using Firefox 102.14.0esr (64-bit) - older and subsequent browser versions may work differently.