Interesting , we are having the same problem with just one of our robots.  The schedule had been running fine upto 18/01.  SInce this date the schedule hasn't run.  I've run through the checklist on the FAQ and it appears ok.
I'm thinking about restarting the application server , BUT i've never done this.  I know when you restart the robots you need to run the Blue Prism - Resource PC.  Do i need to do something similar on the application server ?