Hi @SirFaksalot
The process of uploading a file to SharePoint via Graph API involves sending a request to the SharePoint Graph API endpoint. Before sending a request to the SharePoint Graph API endpoint, the developer must authenticate and authorize the request using Microsoft's authentication mechanism based on OAuth 2.0 protocol. This involves obtaining an access token that allows the developer to access the required SharePoint site. You can follow the steps to Register your App in Azure Portal
https://learn.microsoft.com/en-us/sharepoint/dev/solution-guidance/security-apponly-azuread
Here is a similar issue with yours, please make a reference
If the answer is helpful, please click "Accept Answer" and kindly upvote it. If you have extra questions about this answer, please click "Comment".
Note: Please follow the steps in our documentation to enable e-mail notifications if you want to receive the related email notification for this thread.