Requests got 404 error but work in Graph Explorer

[AlbertZick]

Hi ,
I'm trying to modify the code to learn Microsoft Graph API. When I send any requests that target is a file in Document Library in SharePoint, I get the 404 responses with 'message': 'The resource could not be found.'. However, I check the requests in Graph Explorer, and I get 200 responses. I use a business account, and I had set all permissions that need for file accessing.
The requests I used
GET https://graph.microsoft.com/v1.0/sites/xxxx/drives/<drive_id_1>/root:/<existing_path>/
GET https://graph.microsoft.com/v1.0/drives/<drive_id_1>/items/<item_id_1>/

Additionally, I check the following request and get different response from the Graph Explorer
GET https://graph.microsoft.com/v1.0/drives/<drive_id_1>/root/children

• The response for my code (the value field is empty)
  {'@odata.context': "https://graph.microsoft.com/v1.0/$metadata#drives('<drive_id_1>')/root/children", 'value': []}
• The response in Graph Explorer (the value field is not empty)
  { "@odata.context": "https://graph.microsoft.com/v1.0/$metadata#drives('<drive_id_1>')/root/children", "value": [ { "createdDateTime": "2018-12-20T18:04:06Z", "eTag": "\"{xxxx},1\"", "id": "xxxx", "lastModifiedDateTime": "2018-12-20T18:04:06Z", "name": "xxxx", "webUrl": "xxxx", "cTag": "\"c:{xxxxx},0\"", "size": 545056, "createdBy": { "user": { "email": "xxxx", "id": "xxxx", "displayName": "xxxx" } }, .... }, .... ] }

[AlbertZick]

I'd like to close this issue as I haven't encountered it now, and I don't know why