Error: Forbidden Zopim.com api call

Hello,

one of my agents is trying to make the below get call to our chat api:

https://www.zopim.com/api/v2/chats/search?q=tags:cmac_deleted

they are getting the below error with the existing key that has worked for 2 years and a new key we generated to troubleshoot. We are using OAuth 2.0 with  the header prefix set to bearer_token parameter. I was able to replicate the error in postman. Please advise.

{'error': 'Forbidden', 'description': "You don't have the permission to access the requested resource. It is either read-protected or not readable by the server."}