Hello. My name is***** will assist you with your question.
It shouldn't be disabled at all as far as I'm aware. I don't know of anything that could actually do that. But just make sure that your following these steps to make the link:
Select the text or image you want to become a link.
If the Link inspector isn’t open, click Inspector in the toolbar and click the Link Inspector button.
In the Link inspector, click Hyperlink.
Select the “Enable as a hyperlink” checkbox.
Choose an option from the Link To pop-up menu:
Is it possible that you are doing the book of format that does not support links?
Webpage: Enter a URL.
Email Message: Enter the email address and subject line.
Bookmark: Choose a bookmark from the Name pop-up menu.
If the Name pop-up menu is empty, add bookmarks as described below.
Figure: Click a figure in the Name list. To view only specific types of figures (for example, all movies or galleries), choose an option from the Style pop-up menu.
Chapter or Section: Choose an option from the Chapter pop-up menu.
Page Number: Enter a page number.