Hello @Neil Stephens ,
From the attached screenshot of token scope, it seems you are using delegated permissions. As per the referred document this API is currently supported only using application permission,
Also please note that Subscriptions on onlineMeetings require the encryptionCertificate and encryptionCertificateId property when creating a subscription for notifications with encrypted resource data.
Please refer to this document to generate a token.
Hope this helps.
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