Internal Cross-linked pages not parsed into PDF

[ghost]

URLS list on one page linking to other pages in same book are ignored resulting in links being treated as external URL's.

Is there a way I can fix this?

[josieg]

To add to this report,

Description

From what I can find, internal links created by a person do not work in mPDFs. However, the internal links generated by the table of contents do work, and external links do work.

Expected behaviour
When I create an internal link to another part of a book in Pressbooks, I expect that link to work when I click it in the mPDF format and for it to take me to the approperiate place (either to the correct chapter or to the matching anchor tag)

Actual behaviour
When looking at a book in mPDF format, text that has been set as an internal link will appear blue. However, when I scroll my mouse over it, I am given no option to click it. When I click the text, nothing happens.

Steps to Reproduce

1. Create an internal link with a matching ID in Presbooks (I tried this with an internal link within a chapter, and one between chapters, neither worked).
2. Sample internal link, same chapter, with a matching anchor tag somewhere: <a href="#1">Here is an internal link</a>. Sample internal link, between chapters: <a href="/mpdftesting/front-matter/introduction/">Here is an internal link</a>
3. Export book as mPDF.
4. Find internal link in mPDF.
5. See that the internal link appears blue. Try to click it. Nothing happens. Sad times.