Generally, if the rear washer jet isn't working, it'll be one of three causes:
1) The washer fluid is low.
2) The jet is frozen.
3) The jet is blocked.
My wife's Fiesta had a very similar problem. I could hear the pump running and the washer bottle was full. I disconnected a pipe near the bottle and washer fluid came spurting out. I disconnected the pipe at the jet on the tailgate and once again, washer fluid pumped out fine, so I knew it was the jet itself, which I cleaned out with some lime-scale cleaner, a brush and a pin.
The moral off the story is that it's likely to be something simple, so go through everything methodically, ruling things out as you go.
Hope this helps (and apologies if it looks like I'm trying to teach anyone to suck eggs - that's not my intention!).
Kind Sir, Your egg sucking tutorial has saved me some time by pointing me to a known variable. Unknown until I found your post. I'm hoping my 2012 Focus SEL 5 door has the rear washer tube running along the roof. Solution does not pump onto the rear windscreen but I hear it running and it's full and the jet is not clogged. However, I have had to make a headliner adjustment for a vibrating noise in cold weather and will look there first before I remove the RF inner fender liner to start the methodical diagnostics of the tubing. I didnt really want to bump the thread but did not want to PM as there would be no context. Thanks from the country without a government but I bet the spies are still hard at work.