An agent does not go to work state after handling a call if the agent presses the Ready button while in talk state.
In addition, if the agent services multiple Contact Service Queues (CSQs), auto work may not be configured for each CSQ. The agent only goes to work state if the call comes from a CSQ where auto work is enabled.
For more information about resolving Cisco Customer Response Applications (CRA) and Customer Response Solutions (CRS), refer to these document:
http://www.cisco.com/en/US/products/sw/custcosw/ps1846/prod_troubleshooting_guide_chapter09186a0080193f35.html