Operation: Create; Exception: [Status Code: Unauthorized; Reason: ]

Hello. I encountered a problem when trying to create a functionality that will allow a user to subscribe to the Outlook email collection functionality. I am doing this functionality in a Nest JS application. I have successfully implemented the user authorization processes via Outlook, access token validation via the application webhook, but I get the error "Operation: Create; Exception: [Status Code: Unauthorized; Reason: ]" when making a POST request to https://graph.microsoft.com/beta/subscriptions. I have issued all the necessary accesses, such as Mail.Read, Mail.WriteRead and others, in Azure. What could be the problem?