I work in Public Relations. It has been already 11 years now, building a database of 7,235 people interested in receiving my emails. I joined Constant Contact two weeks ago, sent out this campaign and these are some of the issues I am finding:
1. Before I used to have 100% open rate, sending only text. Now we have added some images and links and the open rate has been only 20%.
2. We went through the "Did not open" contacts and found contacts that did have open the email. So we don't understand if there is a mistake in the system that traces the emails or what.
I am sorry to hear that you are not having the open rate success that you are used to seeing. I did take a look over your campaign, and I believe it is a great email. Having images and links usually helps with open rates, because they help engage your readers.
The reason you may have seen a few people on the Did Not Open list, is due to the fact not all opens are tracked. In email clients like Outlook, where a reader can preview the email on side pane, it will not track as an open unless they click on the email name and it pulls up as a full window.