We got this error for a remote Mitel phone which setting was changed to point to the SRC IP. When rebooting the phone it gets stuck with the message "TW license must be installed".
The message refers to the phone not registering on the teleworker. The SRC is based on the Teleworker so it still reports the phone needs to be registered on the SRC.
Note: The phone's IP must be on the same range as the SRC server (it must be local).