jhullin's account

Support helped me troubleshoot this. For posterity, I was using the wrong URL to create the AuthenticationClient. Below is the corrected block of code.

EslClient esl = new EslClient(API_KEY, "https://sandbox.e-signlive.com/api");
String authToken = esl.getAuthenticationTokensService().createSenderAuthenticationToken(packageId);
AuthenticationClient client = new AuthenticationClient("https://sandbox.e-signlive.com");
String url = client.buildRedirectToDesignerForSender(authToken, packageId);