Follow these steps to troubleshoot images not displaying in Outlook:

1. Check Formatting: Make sure images are in the correct file format for Outlook (.jpg, . gif, and .png).
2. Check Size: Make sure the size of the images isn't too large; reduce size as needed.
3. Check Security Settings: Outlook has a default setting that blocks the automatic display of images in emails.
4. Check Sender's Email: Make sure the sender's email address is in the user's trusted list.
5. Check Image Links: Make sure images are linked properly and from a secure website.