In PDF links are created while designing the PDF and they are actually defined before exporting. Yet some advanced Desktop PDF readers can detect such texts that look like URLS and convert those text-URL to links, not every. You can see that those text-URL links don’t work in mobiles and Mozilla Firefox readers.
We suggest defining the links explicitly so that they work as expected everywhere. Attaching a PDF that explains such links.
How to Check:
Adobe Reader converts URLs to link automatically by default. This feature gives an impression that the URLs are actually working while they are not actually a link in PDF.