What is the issue?
PDF/UA > Logical Structure > Role mapping > Role mapping of non-standard structure types > Non-standard structure type "Story" is neither mapped to a standard structure type nor to another non-standard structure type
What does it mean?
Every non-standard structure type has to be mapped to standard structure type. This mapping is missing in your document.
How to fix it?
For the non-standard structure type "Story" the correct standard type is "Sect".