If the Meet-me Conference fails with a reorder tone, perform these steps:

If this procedure is followed to initiate a Meet-me Conference, or someone joins a Meet-me Conference by dialing the Meet-me Conference number and the call fails with a reorder tone, check if the Meet-me directory number belongs to any partition.

http://www.cisco.com/en/US/products/sw/voicesw/ps556/products_tech_note09186a008009476a.shtml

If the Meet-me directory number belongs to a partition, verify that the IP phone's calling search space (the IP phone that initiates or joins the Meet-me Conference) includes the partition where the Meet-me directory number is assigned.