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I'm going to start with the basic question to collect a bit more information. How did you change the google password ***** your mac? Through the google website?
If you will pick a device, (and let me know what it is), and I'll walk you through the steps to reset the password ***** that device. I have a feeling you have completed all these steps based on your initial information but it gives me a good starting point for troubleshooting.
Additionally, Do you have google 2 factor auth turned on? That can cause additional headaches during a password ***** as one-time passwords are also forgotten.