so it did work for me with curl, then I had to see what made it work, it seems the html formatting was the issue, not sure why it stopped working now from Apple's side, but I was able to make it work by changing my C# code from this: NameValueCollection queryParams = HttpUtility.ParseQueryString(""); queryParams["filter[frequency]"] = "DAILY"; queryParams["filter[reportDate]"] = day.ToString("yyyy-MM-dd"); queryParams["filter[reportType]"] = "SALES"; queryParams["filter[reportSubType]"] = "SUMMARY"; queryParams["filter[vendorNumber]"] = VendorId; queryParams["filter[version]"] = "1_0"; to this: string url = $"https://api.appstoreconnect.apple.com/v1/salesReports" + $"?filter%5Bfrequency%5D=DAILY" + $"&filter%5BreportDate%5D={day:yyyy-MM-dd}" + $"&filter%5BreportType%5D=SALES" + $"&filter%5BreportSubType%5D=SUMMARY" + $"&filter%5BvendorNumber%5D={VendorId}" + $"&filter%5Bversion%5D=1_0";

Same for us, it's been running for years, it stopped working 2~3 days ago, returning 400 with no further explanation

Much Needed !