I want to add a link to a resource where the user can upload a large file.
When I edit this message using 'phrases', the link inside it doesn't work.
The HTML code doesn't work either. How can I fix this?
Roughly speaking, not all phrases accept HTML. The safest rule of thumb is really that unless the default phrase includes HTML, it's not necessarily safe to add HTML to it.
In this case, you may need to edit the widget HTML itself to add the link.