IOS gateways support UDPTL for t.38 only and it doesn't support SRTP. If you want SRTP to work for faxing then you should use passthrough (modem NSE based passthrough for faxing b/w cisco gateways and protocol based fax pass-through for interop b/w cisco and another PBX/vendor). Cisco fax relay also supports SRTP for faxing but it is out dated and not supported on ISR G2 routers.
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.