1. This is the full tracking of your parcel:
China Post Register Air Mail Tracking System
Parcel No.RR906312417CN tracking result
2016-08-19 17:00:55.0 Guangzhou city 流花Post Office received
2016-08-19 17:13:17.0 Guangzhou city 流花Post Office customs scan
2016-08-19 17:29:08.0 leaving Guangzhou city 流花Post Office ，next station Guangzhou Airport
2016-08-21 09:21:54.0 Guangzhou Transit Station export security scan
2016-08-21 14:33:11.0 Guangzhou Transit Station export customs cleared
2016-08-24 21:48:00.0 arrive Guangzhou Airport
2016-08-26 22:04:59.0 leaving Guangzhou Airport going to next airport/seaport
2016-09-03 13:10:00.0 Langley export customs cleared
2016-09-07 10:07:32.0 Beijing Transit Station import customs scan
2016-09-07 15:32:57.0 Beijing Transit Station import customs cleared (domestic transit )
2016-09-10 14:56:14.0 Guangzhou Transit Station import customs scan ,remark (rejected )
2016-09-11 14:47:31.0 Guangzhou Transit Station import customs cleared (domestic transit )
2016-09-12 18:22:50.0 arrive 体育东路 Delivery Office delivery office
2016-09-13 09:32:57.0 体育东路 Delivery Office attempt delivery
2016-09-13 11:03:25.0 体育东路 Delivery Office attempt delivery
2016-09-13 17:44:30.0 体育东路 Delivery Office attempt delivery

2. For whatever reason your parcel was return to China from UK. You should contact seller as soon as possible to tell him and provide him with the above tracking so he knows what you are talking about.

Hope this help.