Core Issue
There are either Calling Search Space/Partition issues, or Fast Dial may not be configured correctly.
Resolution
If dialing the number without Fast Dial works, ensure that you have added any dial prefixes required in your Fast Dial settings. For example, many enterprises require users to dial 9 to reach an outside line.
If dialing the number without Fast Dial does not work, check that you are in the correct Calling Search Space/Partition. You must be in the proper space to be able to call certain numbers. For more information, please refer to Understanding and Using Partitions and Calling Search Spaces With Cisco CallManager 3.0.