Second installation of device fails

I have a umdf2 serial driver. I could install device using DeviceManager>>Add Legacy Device option. The first installation of first device is success. When installing another device instance , it is failing and shows Code 31 - CM_PROB_FAILED_ADD. But it is listed in device manager with error status. when in disable and enabled it, it is working. Any idea on this?

Failed add means your driver was loaded and returned failure from AddDevice. You need to debug your driver.

Ok Thanks!