Too long to a comment.
Seem that the real question is related with How to show header on first page of chapter? and have been solved here and in the comment of Johannes_B above, but what is really asked (Why is there no header?) is the important isssue and a recurrent question here. It worth explain as rightly has been asserted, why is wrong a header in a title page or starting a chapter.
What is the purpose of a header? Is not other that provide a quick help to the reader about the document structure: mainly pages, main section level/s and author when is not the same in all chapters, so you can understand instantly where you are.
But first page of a chapter, not to say a title page, have already a huge title at and author in a prominent place. Repeat again this information in the upper margin does not help at all. It is enough clear where you are. The only result is tarnish the main titles of the book, losing the space above. Seem that many people often do not realize how important is this (another recurrent question is how to reduce the upper margin in first chapter pages). Either the chapter titles deserve prominent places, or there are no reason to make a book but an article or something in between (memoir, report). In page with the title of the document this never have sense, whatever the document is.
Excruciatingly, many times you are asked to use a ugly document layout. What to do then?
1) Ignore it. It could be only a recommendation, or the infraction of the rule finally does not matter at all when the result is better.
2) Try to explain why it should not be done, if you tried, but the brute supervisor is not dazzled by the good typography of your draft.
3) Finally, if your suggestions is rejected or unlikely they will be accepted (e.g. using official thesis or book templates of some University or important editorial) well, ehhh, ... when in Rome, do as the Romans do, but do not become a legionary. People used to bad typography tend to think that is how it should be.
\thispagestyle{fancy}will get you the header. But i think using a header on the title page is wrong. That is why i linked to an answer, that explains how to design your own titlepage. – Johannes_B Feb 04 '18 at 08:27