400 response when posting Checkout request to Google Checkout API

[Juls3]

While I've integrated several payment processors and shopping carts in the past, this Google Checkout API integration is not going well for me. I get a 400 response from Google, even when I use the diagnostic link. I'm sure something's wrong in my URL, but I can't seem to figure out what. I'm using a sandbox Merchant ID and Key.Can someone help me see what I'm doing to get this 400 response, please?I am using Java and posting from a server thus I'm calling the server to server API link:\[code\]https://sandbox.google.com/checkout/api/checkout/v2/merchantCheckout/Merchant/%SANDBOXID%<?xml version="1.0" encoding="UTF-8"?><checkout-shopping-cart xmlns="http://checkout.google.com/schema/2"> <shopping-cart> <merchant-private-data> <merchant-note>8Ra8fw4tBaOdP4v3lseykKO6crR0dFqhzWV0EmqKuVuQaN1w0mcScAAR71pbexXlVnrwpP8wNzehuc7wz3KO9JM6xfedW8106olarCZcZBs=</merchant-note> </merchant-private-data> <items> <item-name>MyName : MySubname</item-name> <item-description>Weigh in on this year's...</item-description> <unit-price currency="USD">100</unit-price> <quantity>1</quantity> </items> </shopping-cart></checkout-shopping-cart>\[/code\]I am using Java to post this data. In the code below, the url above is sandboxLink in the code and checkReq is the XML post...\[code\] public static String postCheckoutReqData(String userID, String gameName, boolean test) { String checkRequest = GoogleCheckoutXML.getCheckoutRequestXML(userID, gameName); if(checkRequest.indexOf("error,") != -1) return checkRequest; URL url = null; try { String baseCodeString; if(test) { url = new URL(GoogleCheckoutXML.sandboxLink + GoogleCheckoutXML.sandboxMerchID); baseCodeString = GoogleCheckoutXML.sandboxMerchID + ":" + GoogleCheckoutXML.sandboxMerchKey; } else { url = new URL(GoogleCheckoutXML.productionLink + GoogleCheckoutXML.merchantID); baseCodeString = GoogleCheckoutXML.merchantID + ":" + GoogleCheckoutXML.merchantKey; } //url = new URL(GoogleCheckoutXML.diagnose); byte[] bytes = (baseCodeString.getBytes()); baseCodeString = new Base64().encodeAsString(bytes); URLConnection conn = url.openConnection(); conn.setDoOutput(true); conn.setRequestProperty("Authorization", "Basic " + baseCodeString); conn.setRequestProperty("Content-Type", "application/xml; charset=UTF-8"); conn.setRequestProperty("Accept", "application/xml; charset=UTF-8"); OutputStreamWriter wr = new OutputStreamWriter(conn.getOutputStream()); wr.write(checkRequest); wr.flush(); // Get the response BufferedReader rd = new BufferedReader(new InputStreamReader(conn.getInputStream())); String line; while ((line = rd.readLine()) != null) { line = line + rd.readLine(); } wr.close(); rd.close(); return line; } catch (Exception e) { e.printStackTrace(); return "error,Purchase Error posting communcation failed"; }\[/code\]The actual stack trace in Tomcat is:\[code\]java.io.IOException: Server returned HTTP response code: 400 for URL: https://sandbox.google.com/checkout/api/checkout/v2/merchantCheckout/Merchant/[withheld]at sun.net.www.protocol.http.HttpURLConnection.getInputStream(HttpURLConnection.java:1612)at sun.net.www.protocol.https.HttpsURLConnectionImpl.getInputStream(HttpsURLConnectionImpl.java:254)at com.[withheld]..GoogleCheckoutXML.postCheckoutReqData(GoogleCheckoutXML.java:194)at com.[withheld]...l.getCheckoutLink(DubQueryImpl.java:270)at com.[withheld]....GenerateCheckoutLinkServlet.doGet(GenerateCheckoutLinkServlet.java:56)at com.[withheld]...doPost(GenerateCheckoutLinkServlet.java:73)at javax.servlet.http.HttpServlet.service(HttpServlet.java:641)at javax.servlet.http.HttpServlet.service(HttpServlet.java:722)at org.apache.catalina.core.ApplicationFilterChain.internalDoFilter(ApplicationFilterChain.java:305)at org.apache.catalina.core.ApplicationFilterChain.doFilter(ApplicationFilterChain.java:210)at org.apache.catalina.core.StandardWrapperValve.invoke(StandardWrapperValve.java:225)at org.apache.catalina.core.StandardContextValve.invoke(StandardContextValve.java:123)at org.apache.catalina.authenticator.AuthenticatorBase.invoke(AuthenticatorBase.java:472)at org.apache.catalina.core.StandardHostValve.invoke(StandardHostValve.java:168)at org.apache.catalina.valves.ErrorReportValve.invoke(ErrorReportValve.java:98)at org.apache.catalina.valves.AccessLogValve.invoke(AccessLogValve.java:927)at org.apache.catalina.core.StandardEngineValve.invoke(StandardEngineValve.java:118)at org.apache.catalina.connector.CoyoteAdapter.service(CoyoteAdapter.java:407)at org.apache.coyote.http11.AbstractHttp11Processor.process(AbstractHttp11Processor.java:1001)at org.apache.coyote.AbstractProtocol$AbstractConnectionHandler.process(AbstractProtocol.java:585)at org.apache.tomcat.util.net.JIoEndpoint$SocketProcessor.run(JIoEndpoint.java:310)at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1110)at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:603)at java.lang.Thread.run(Thread.java:722)\[/code\]