1. The parcel is going back to the seller, here is a tracking that you can understand:
http://www.track-chinapost.com/track.php?code=RF238865333CN&fc=0

Number: RF238865333CN
Package Status: Expired
Destination Country: Unknown
Origin Country: China
2016-07-30 10:10 The Shenzhen Exchange Bureau, import each other (internal transit)
2016-07-30 09:40 The Shenzhen Exchange Bureau, import opening
2016-07-24 13:35 Beijing Exchange Bureau, import each other (internal transit)
2016-07-24 09:55 Exchange Bureau in Beijing, has imported opening
2016-07-20 08:11 In New York, has been exported
2016-05-09 09:57 The Shenzhen Exchange Bureau, have been exported directly
2016-05-08 23:54 The Shenzhen Exchange Bureau, have been exported to open
2016-05-08 23:04 Small package Center, left, next stop "Center in Shenzhen"
2016-05-08 19:27 Parcel centre
2016-05-08 15:38 Small package Center, has received send
2016-05-02 08:57 Electronic information has been received

2. According to this:
2016-07-20 08:11 In New York, has been exported
2016-05-09 09:57 The Shenzhen Exchange Bureau, have been exported directly

Your parcel was going to USA around the 09 May and on the 20 July it was exported to China coming back to possibly the seller.

3. What was wrong with the parcel? That is the big question, was the address wrong, was there missing something in the address, was there something inside the parcel that was not allowed in USA. All those questions I can not answer. Maybe the seller could answer them as soon as he gets the parcel.

4. Now the last tracking of the parcel is this:
2016-07-30 10:10 The Shenzhen Exchange Bureau, import each other (internal transit)

Meaning is transiting to another location possibly the seller address.

5. I'm providing you with the full tracking of your parcel from China Post:

China Post Register Air Mail Tracking System
Parcel No.RF238865333CN tracking result
2016-05-02 08:57:23.0 Electronic Data Received
2016-05-08 15:38:18.0 parcel center received
2016-05-08 19:27:35.0 parcel center customs scan
2016-05-08 23:04:17.0 leaving parcel center ，next station Shenzhen center
2016-05-08 23:54:31.0 Shenzhen Transit Station export security scan
2016-05-09 09:57:20.0 Shenzhen Transit Station export customs cleared
2016-07-20 08:11:00.0 纽约 export customs cleared
2016-07-24 09:55:12.0 Beijing Transit Station import customs scan
2016-07-24 13:35:16.0 Beijing Transit Station import customs cleared (domestic transit )
2016-07-30 09:40:41.0 Shenzhen Transit Station import customs scan
2016-07-30 10:10:08.0 Shenzhen Transit Station import customs cleared (domestic transit )

You should contact seller and give him the above tracking and say to him that the parcel is returning back. You will need to have some sort of arrangement with him about your parcel.

Hope the above information will help you.