This issue is a special case of a one-way voice issue. Specifically, users can hear prompts, but they cannot record.
To troubleshoot this issue, perform the following steps:
Verify that there is not a Unity wave problem by checking the NT event log for wave error messages.
Verify that Real Time Protocol (RTP) data is being sent.
Verify that the network is not dropping packets.
Verify that a firewall is not dropping packets.
Verify that dual active NICs are not being used on the Unity system.
Note: A variation of this problem may occur as follows: Cisco Unity answers a call, but the users cannot hear Cisco Unity. This issue may be due to RTP packets traversing from the IP phone to Cisco Unity, but not from Cisco Unity to the IP phone.