MWI suddenly not working

[djshahzad]

I have Unity 3.1 & CCM 3.2 + IVR 2.2, all were working fine but since a day on IP Phones, MWI are not working but still users can receive voice mails from the system.

I have checked that

Can anyone guide me to resolve this problem as soon as possible please?

[Hin Lee]

Start with this doc:

http://www.cisco.com/en/US/products/sw/voicesw/ps2237/prod_troubleshooting_guide_chapter09186a00801d6d30.html