Text links do not work

I am trying to insert a URL link to a piece of text in a paragraph block - for example: click here to learn more where "here" is hyperlinked to an external webpage. When previewing or reviewing the course from the same device that created the course (laptop), the links work. But from other devices (e.g. smart phone, other computers outside of my company network), the links do not work. No error message, though, but also nothing happens at all when clicking on the links. 

Any thoughts? Thank you in advance for your help.