I am trying to get all the applications installed on all the devices using microsoft graph API

I’m currently working on a script that sends a custom notification to a company portal via Microsoft Graph API. I am using the Graph Explorer to test the API request to https://graph.microsoft.com/beta/deviceManagement/comanagedDevices/{managedDevice-id}/microsoft.graph.sendCustomNotificationToCompanyPortal. Despite having already granted the necessary permissions, as confirmed by Microsoft’s documentation heretext, which states that only two permissions are required, I am still encountering a “403 Forbidden” error.