Howdy @Anonymous ,
The Error\Status Code is 403 - Forbidden.
- Navigate to Graph Explorer in your browser.
- Login with Office 365, credentials and provide the ‘Consent on behalf of your organization’ an click on ‘Accept‘.

To isolate the problem, can you please Test the same REST request using a REST client such as PostMan or ARC.
On a side note for graph API I prefer using 'HTTP with Azure AD connector'

You can find some details in my blog, https://clavinfernandes.wordpress.com/2020/05/04/exporting-chats-from-microsoft-teams-using-power-automate/
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