So, I discovered, by accident, that the little bell icon next to people's diary names wasn't working. It probably hasn't been working for a couple of weeks if not more... Anyway, it works again now!
As a result of fixing that bug, I deployed it to the live server - which then broke the Redis caching server (for some odd reason best known only to itself). I've adjusted its attitude with a slight code tweak and redeployed and now that's working again. Unfortunately it would have meant that if you tried to get to your dashboard in the past few hours you wouldn't have been able to.
All should now be working again - but if you find something that isn't please drop me a line.