Thanks for the response.
Please note, since Aspose.Cells Cloud 19.9 we have introduced a new API Version V3. It uses JSON Web Token(JWT) for API request authentication. Now updated sample cURL and C# code is as follows. Please feel free to contact us for any further assistance.
curl -X GET "https://api.aspose.cloud/v3.0/cells/Book1.xlsx/worksheets/Sheet4/charts/0?format=png&folder=Temp" -H "accept: multipart/form-data" -H "authorization: Bearer [Access_Token]" -H "x-aspose-client: Containerize.Swagger"
string name = MYDOC; string sheetName = SHEET3; int? chartNumber = 0; string folder = TEMPFOLDER; string format = "png"; var response = cellsAPI.CellsChartsGetWorksheetChart(name, sheetName, chartNumber, format, folder);