I’m using hype professional 3.6.3 and affinity designer for creating svg-objects. Some of the objects i can see in hype, but in preview or later in the exported widget for iBooks they are not shown. More precisely they are sometimes visible an sometimes not.
If you could share your SVG, affinity designer file, and the Hype document that would be great. Some complex SVGs might not be exported in a format that iBooks likes.