Sometimes Cfengine refuse to run on a new client and simply does not explain what the problem is. The error message (which you only see when running cfagent with -v) looks like this: 
cfengine:client:/var/opt/dsau/cfengine/inputs/update.conf:194: Warning:
actionsequence is empty
cfengine:client:/var/opt/dsau/cfengine/inputs/update.conf:194: Warning: perhaps
cfagent.conf/update.conf have not yet been set up?
The message "actionsecquence is empty" really means that the cfagent.conf is empty, because it could not be retrieved. The question then is why couldn't it be retrieved. Here is a check list:
  1. update.conf is somehow broken
  2. Master host cannot be contacted in network
  3. Master host and client believe the hostname to be a different IP
In my case the problem was caused by the #3 due to different /etc/hosts the hostname did not resolve into the same IP as on the cfengine master. Usability of cfengine sucks...