The reason you cannot access the TOC in the "Canada's System of Justice" document is that it simply doesn't have one. What you see there are internal links overlaying the 'printed' TOC but the document doesn't have an 'embedded' TOC.
You can check that by opening the document with a PDF viewer on your PC. Then try with this
example document.
So it appears that Onyx Neo Reader does not support links in documents but TOC works perfectly fine.