The first (DAT in ePO not reflected) comes from the general agent to server communication, you should look at the local agent log for communication errors to the ePO server.
For example on windows 7: c:\users\all users\mcafee\common framework\db\agent_<machine>.log
Where <machine> is the name of the local machine.
For systems that communicate, but do not update that is actually a different mechanism.
There may still be errors recorded in the agent_<machine>.log but the main detail for updating would be found in the mcscript.log (c:\users\all users\mcafee\common framework\db\mcscript.log)
When you find some error messages, you can search their meaning in the McAfee Knowledge Center: