List calendar events from specific user using MS Graph API

We are trying to run some Arduino code that lists all events from the calendar of a user in our Azure AD.
There are some issues with the permissions as one of us is able to get the data using the Graph explorer but not when authenticated using the Arduino code.

We have set up a App registration in the AAD with the necessary API permissions as seen below (we weren't sure if it was Delegated or Application so we added both, though I am fairly certain it is Delegated seeing the scope that the token is using) API permissions

We are using the Application (client) ID and Directory (tenant) ID for authentication together with a login. During the setup we need to go to https://microsoft.com/devicelogin and use a code to authenticate the Arduino.

The library we're using is ArduinoMSGraph@^0.2.0

This function is used to set the scope
graphClient.startDeviceLoginFlow(deviceCodeDoc, "offline_access%20openid%20Presence.Read%20Calendars.Read%20Calendars.ReadBasic%20Calendars.ReadWrite");

According to the access token the scope is also approved (together with some other scopes we used while testing)
Here is that part of the decoded token. I used https://jwt.ms/ to decode it.
scope

This function is called to do the GET request
bool res = requestJsonApiButDifferent(responseDoc, "https://graph.microsoft.com/v1.0/users/<user>@<tenant>.nl/calendar/events", "", "GET", true);
(This is a slightly altered version of the original requestJsonApi() because there were some issues with parsing the JSON data but it works just fine for other GET requests so the edit shouldn't be an issue for the authentication. You can find my version of the function here)

And that seems to work fine to get the Presence but when trying to access the calender events for another user we are unable to do so.

The error we get when running the above mentioned GET is
requestJsonApi() - Other HTTP code: 403
The JSON repsonse is

{
    "error": {
        "code": "ErrorAccessDenied",
        "message": "Access is denied. Check credentials and try again."
    }
}

This means it has to be an issue with the permissions and we guess it's in the API permissions for the Application in the AAD but this is were I'm stuck.
We followed multiple guides that tell me to grant Admin consent, which we did with the API permissions (as seen above) and with the Enterprise permissions.
enter image description here

This is where we're stuck. What are we missing?

We would appreciate any input. If I need to provide more information to solve this let me know.

If you are using a DeviceLogin then you will be using Delegate permissions (eg the credentials of whatever user is authenticating).

Probably your issue is that you haven't given Calendars.Read.Shared Delegate permission as this will allows you to read calendars of users other then the user that is logging on that this particular user has been granted explicit access to eg(via Outlook delegation or Add-MailboxFolderPermisssion etc).

Turns out that we needed to add the account that logged in on the device (me) to the delegates list on the Microsoft 365 admin center.