Voicera enables Eva to join any Google Meet call, but we do not currently support Google Hangouts. Over recent months, Google has been shifting more users to its Google Meet tool. Below is a link to a great article that explains the status of the switch and what it means for you. Read that article here.
By default, all Google Meet calls are restricted to users inside your organization’s domain. At the start of your Google Meet call, Eva will dial in and the host will need to "Admit" Eva (screenshot below). Read more about this setting on the G-Suite Help Center here.