Unable to generate or upload assets in RPE Document Builder

I have recently set up the RPE Document Builder, and whilst the application appears to be running OK and accessible, I cannot upload any assets (I get the message 'The requested operation has failed') nor can I generate the Ready-to-use sample assets ('Ready-to-use asset creation failed. Check if they are already created.' - they are not). Additionally, the News Keeper sample application does not complete - the page loads but the function does not complete and eventually the message underneath the progress bar simply says 'Error' - so I am guessing there is something fundamentally wrong with the set up despite the application appearing to load OK.

I am using Apache Tomcat to deploy/manage the application service. The Tomcat manager indicates that all the necessary applications are running OK.

Any ideas as to what might be wrong?