{"error":"invalid_grant","error_description":"Please check the 'sub' claim. The 'sub' specified is i

Hi

I am trying to make BOX Connection using App User that I created using enterprise user and I am getting below error

{"error":"invalid_grant","error_description":"Please check the 'sub' claim. The 'sub' specified is invalid."}

Basically below my code snippet

1.Created enterprise api connection as below

BoxDeveloperEditionAPIConnection api =

        BoxDeveloperEditionAPIConnection.getAppEnterpriseConnection(boxConfig, accessTokenCache);

2.Created App user as below

String userName = "appuser1";

    String jobTitle = "App User 1";

    long spaceAmount = ***number removed for privacy***4;

    // Create app user

    BoxUser.Info createdUserInfo = BoxUser.createAppUser(api, userName);

    System.out.println(" App user ID " +createdUserInfo.getID());

3.Now when I am trying to make api connection using user id created in step 2 above , I am getting error mentioned above

 Below is the connection code

String userId = "***number removed for privacy***";

        BoxDeveloperEditionAPIConnection session = new BoxDeveloperEditionAPIConnection(userId, DeveloperEditionEntityType.USER, boxConfig, accessTokenCache);

        String userToken = session.getAccessToken();

        System.out.println("userToken"+userToken);

Can somebody please tell me the reason