In the time since I updated my iPad Air from iOS 7.1.2 to iOS 8.0.0 and then iOS 8.0.2 my keyboard shortcuts have been coming and going, randomly and intermittently.
Sometimes my shortcuts appear in the list (Settings.. General.. Keyboard.. Shortcuts) but they will not work, and sometimes they do work.
There is no CONSISTENT pattern, no rhyme nor reason, that I have been able to correlate with the behavior that I have seen.
My guesses are an intermittent iCloud problem.. there are hundreds of comments about this in dozens of threads on
discussions.apple.com but their search function is so lame most do not show up in the Apple discussions search results.
Try Google. Limit search results to the past month. You will see a lot, more than 150 discussions...
ios keyboard shortcuts site:discussions.apple.com
There are so many workarounds (some may work temporarily for some and not for others, as reported by many other users) this really seems like a random and intermittent bug.
My own suspicions are interaction with the new PREDICTIVE KEYBOARD, or an iOS memory manager problem, or a
random iCloud bug.
IF you make detailed comment about your symptoms at
https://www.apple.com/feedback/
there will be a better chance for us all that it may get fixed.