1. This is the tracking of your parcel:

Number: RM712204671CN
Package Status: In Transit
Destination Country: United States
Origin Country: China
2016-08-08 15:22 Beijing Exchange Bureau, import each other (internal transit)
2016-08-08 09:04 Exchange Bureau in Beijing, has imported opening
2016-08-04 12:51 In New York, has been exported
2016-07-16 15:03 Zhengzhou international shipment
2016-07-15 14:39 Zhengzhou airport, left hand navigation
2016-07-15 14:38 Zhengzhou airport, arrival
2016-07-14 15:16 Zhengzhou Exchange Bureau, have been exported directly
2016-07-14 14:40 Zhengzhou Exchange Bureau, have been exported to open
2016-07-13 19:20 Bulk mail collection mail processing center, Nanyang city, away, the next stop "Nanyang Centre"
2016-07-13 19:13 Bulk mail collection mail processing center, Nanyang city,
2016-07-13 16:45 Bulk mail collection mail processing center, Nanyang city, has received send

2. For whatever reason your parcel is returning to the seller:
2016-08-08 09:04 Exchange Bureau in Beijing, has imported opening
2016-08-04 12:51 In New York, has been exported
2016-07-16 15:03 Zhengzhou international shipment

3. Either the parcel was refuse entry in USA or your parcel was not able to be deliver. Since the USPS post system does not track China Post Registered Mail we have limited scanning/tracking to understand the reason of the parcel coming back to China.

4. May I suggest you contact seller and tell him the parcel is returning back to him, provide him with the following tracking or any other tracking to make sure he understand the situation.

5. You will have to come to some sort of arrangement with the seller because you have not received the parcel.

Hope this help.

Quote from Max_Ki on August 9, 2016, 20:15
I think my package is stuck, because it is still at one position. The tracking number is RO233170881CN

1. This is the full tracking of your parcel:

China Post Register Air Mail Tracking System
Parcel No.RO233170881CN tracking result
2016-07-23 21:08:22.0 南昌city 包裹快递局 received
2016-07-23 21:10:26.0 南昌city 包裹快递局 customs scan
2016-07-23 22:04:16.0 leaving 南昌city 包裹快递局 ，next station 南昌station
2016-07-24 08:18:47.0 南昌Transit Station export security scan
2016-07-24 10:09:39.0 南昌Transit Station export customs scan (domestic transit )
2016-07-26 20:24:45.0 Shanghai Transit Station export security scan

2. May I suggest you read this:
What does the status “Export Security Scan” mean? How long it will take?
On this site:

What does the status “Export Security Scan” mean? How long it will take?

Hope this help.