In our organization we have Lync tied to unified messaging in exchange.  It is working fine for all my users but for one of them when you go to his phone and select voicemail you see " your account is not configured for Exchange Unified Messaging."  But, it is enabled in Exchange EMC and tied to the same dial plan the rest of my working users are in.  I do notice under UM settings for this user the SIP address: shows "null" and the others do not.  Although the user has an SIP address in Lync and if you go to their email addresses in exchange they have an SIP address listed there as well.... Any ideas to point me in the right direction on what is going on?

Thanks

Does the EUM addresses listed for the mailbox match the EUM addresses for another working mailbox?  Is the account hidden from the GAL or disabled in any way?

Also, although this is the correct forum to post this in, it doesn't get paid a lot of attention.  If you post in the Lync forums sometimes you'll get more eyes on the issue.