The token contains no permissions, or permissions can not be understood.

How have you obtained the access token? If you used https://login.microsoftonline.com/{tenant-id}/oauth2/v2.0/token is the user in the same tenant?

Yes, the user is the same tenant. Any other possible issue.

{"error":{"code":"NoPermissionsInAccessToken","message":"The token contains no permissions, or permissions can not be understood.","innerError":{"oAuthEventOperationId":"db6309f5-0cbe-488b-8ab1-c50cf41e06ed","oAuthEventcV":"3KPbLlLuPk66QZv9dzgJHw.1.1","errorUrl":"https://aka.ms/autherrors#error-InvalidGrant","requestId":"f85016c4-ff4a-40ea-bdc1-e33b2c2879a

This error is commonly associated with access token and how it was acquired. To find out what this error is associated with, you will have to provide more datils.

• How you are acquiring the access token. Provide the details of oauth flow used and the token request call.
• Then test out if this issue only happens for one user or all users
• Also is the app registration multitenant or single tenant.

How you are acquiring the access token. Provide the details of oauth flow used and the token request call.

---https://login.microsoftonline.com/a1cd3436-6062-4169-a1bd-79efdcfd8a5e/oauth2/v2.0/authorize?response_type=code&client_id=403a1dca-c4f5-4296-99da-25d7094096df&redirect_uri=https%3A%2F%2Fkaseya--crmitdev.my.salesforce.com%2Fservices%2Fauthcallback%2FMaxNetOutlook&scope=User.Read+User.Read.All+User.ReadWrite.All+User.Invite.All+Calendars.Read+Calendars.ReadWrite+openid+email+profile+offline_access+Calendars.Read.Shared+Calendars.ReadWrite.Shared+Place.Read.All&state=CAAAAXmin1VNMDAwMDAwMDAwMDAwMDAwAAAA5jd50IUCTDJcEWVXWtwKRbfVSbh&sso_reload=true

Then test out if this issue only happens for one user or all users

--- All users

Also is the app registration multitenant or single tenant.

-- Accounts in any organizational directory (Any Azure AD directory - Multitenant) and personal Microsoft accounts (e.g. Skype, Xbox)