Hi Hillary,
Image-open tracking, as I describe above, may work for many recipients, but it simply cannot be relied upon to work for every recipient. Even a single recipient that refuses to display images will not be counted or some clients may be problematic look below:
Outlook — By default, images aren't downloaded due to security, May not work until recipient downloads the emails
Gmail — Will work if you are landing in the inbox.
Mobile — Mobile email applications download the pixel by default as soon as the user opens your email so this will work if you are landing in the inbox.
Can you post/send the code that you have implemented? looks like you are using one tag for open and click.
Regards,
Amit