A user is experiencing an issue when trying to "listen in" on a live call from the web client. They receive the attached error message and are not allowed to perform the action. The cache has been cleared and the computer restarted.
This response appears when another extension is listening in / has barged in to the call already.
Can you also set up a test. Create two new extensions, log in as both of them (the second on an incognito tab for example). Give yourself rights to barge in / listen from the Extension's Rights section. Connect the two extensions on a call and listen in, does this error message show up?