Why do my org DEADLINEs appear with no warning?

Question

I have org-deadline-warning-days set to 14. Here is a deadline in my agenda file:

** TODO Do thing
DEADLINE: <2018-11-20 Wed>

In the agenda view for that date (20th Nov), I see:

next:       Deadline:   TODO Do thing

But no warning of that: for example, nothing on the 6th Nov. I expected that having org-deadline-warning-days would show a warning on that day. Why doesn't it? How can I get a warning?

PS: even if I write the deadline like this:

DEADLINE: <2018-11-20 Wed -1d>

I still don't get any warning (which if I understand should show on the 19th in the agenda view in this case), only an entry in the agenda view on the 20th itself.

Answer 1

The warning only appears when the day of the warning comes around. Before that date becomes today's date, it's not shown.

On a more careful reading of the manual, that's exactly what it says:

Deadlines and Scheduling

In addition, the agenda for today will carry a warning about the approaching or missed deadline

(my emphasis)