On Webex, if you are using a Mac, you can only join one meeting at a time.  If you do not officially leave your previous meeting before attempting to enter another meeting by clicking the Leave red X icon, you will receive this error message:

If this happens, follow these steps:

1. Close the current meeting window with the error message.

2. Go back into the previous Webex meeting you had exited using the link or invitation provided.

3. Exit this meeting using the Leave red X icon, and then select Leave Meeting in the pop-up window.

4. Re-enter the new meeting using the link or invitation provided.