Have you imported the images into Sigil or just referenced to it? You need to add the images into the ePUB.
How do I tell the difference?
I have 100 pics in the images folder of Sigil. I then get to the place that I want to insert the pic and I click add file, then double click my picture and it shows up in both code and in the book mode. Are you saying I have only referenced rather than added?
Here is an example of code that works with the picture being a chapter heading
<h1 style="text-align: center;" title="Little Rag Doll"><img alt="Misericordia Readers Primer_Page_016" src="../Images/Misericordia%20Readers%20Primer_Page_016.jpeg" /></h1>
Here is an example of code that is not working for me.
<p class="s1 s3">She called Baby Boy.</p><img alt="Misericordia Readers Primer_Page_017" src="../Images/Misericordia%20Readers%20Primer_Page_017.jpeg" />