Hi Shams,

This combination is not supported :( Here are the CCM Versions that will work with CUE 2.3.1;

CUE

2.3.1

2.3.2

Compatible Cisco Unified CallManager Releases

4.1(2)

4.1(3)

4.2(1)

4.2(3)

5.0(1)

5.0(2)

5.0(3)

5.0(4)

http://www.cisco.com/en/US/docs/voice_ip_comm/unity_exp/rel2_3/relnote/rncue23.html#wp135836

Support for Cisco Unified Communications Manager 6.1

Cisco Unity Express 3.1 provides interoperability with Cisco Unified Communications Manager 6.1.

http://www.cisco.com/en/US/docs/voice_ip_comm/unity_exp/rel3_1/release/notes/rncue31.html#wp229417

Hope this helps!

Rob