I think this is due to a signaling bug, try waiting 2 seconds more, and you will see that you can pick up the call.
By the way, did you have any problems concerning the VXML part?
My experience was, that the IVRMainpage.VXML was not built correctly, the ip address was not set to the ip address of the Mobility Manager, if you go to the system (via ssh) and browse to IVRMainpage.vxml document, and you edit it, you will have streaming media for the IVR portion of Mobility Manager.
Also it is wise to make sure your DNS is working correctly for the pickup service, (the phone service is looking for the hostname).
This problem is probably due to bug ID CSCef81967.
The way to solve this is to get root access to the and turn off the JTAPI tracing editing the /usr/local/snr/jar/jtapi.ini and set the DEBUG parameter to 0. Then restart the CMM service.
The bad news is that the only way to get root access to the internal folder is using the CLI to create a remote account and then send the passphrase generated to the TAC in order to receive the password for root access using this account.
Are you getting this error “Installer User Interface Mode Not Supported. The installer cannot run in this UI mode. To specify the interface mode, use the -i command-line option, followed by the UI mode identifier. The value UI mode identifiers...
The below trick might come handy when you have to add a new node to a cluster but you don't have or is unsure of the security password for the publisher. This procedure has been around for ages.
1) Login into the CLI of the Publisher.