Do a debug mgcp packets- this will show, perhaps helps in why it was rejected- if it responds with 500 it will be the name of the GW - check if you have domain name set on the gateway e.g -cisco.com if so add it on the CUCM
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.