Hello my fellow SAB community. I just wanted to share something I discovered in case it can be of benefit to someone else in the future… I was befuddled as to why some images would render properly in my app and others would not. After many attempts troubleshooting I discovered that the file name of an illustration can NOT contain a # symbol.
For example, an illustration with a file name of Matt1#1 will not work. SAB will let you add and place the illustration but the viewer will not show the image and the image won’t be built in the app. Matt1-1 works fine. You can also have spaces but cannot # your illustrations. Mystery solved. Hopefully this helps someone else avoid the pain I experienced 
Blessings, in Jesus’ name!