1. You might have given the wrong tracking number, this is what I get with the tracking number provided:
Parcel No.RC451375374CN tracking result
2016-03-17 17:58:45.0 Guangzhou international parcel process center received
2016-03-17 21:28:47.0 Guangzhou parcel process center customs scan
2016-03-17 23:46:42.0 leaving Guangzhou parcel process center ，next station Guangzhou Airport
2016-03-18 09:15:25.0 Guangzhou Transit Station export security scan
2016-03-18 11:23:06.0 Guangzhou Transit Station export customs cleared
2016-03-21 08:32:00.0 arrive Guangzhou Airport
2016-03-21 10:37:24.0 leaving Guangzhou Airport going to next airport/seaport

2. Do you have the right tracking number?

Hope this help

1. I have track your parcel on 3 different sites, this is what I get:
Parcel No.RF272978074CN tracking result
2016-06-13 10:57:53.0 Electronic Data Received
2016-06-14 15:44:11.0 China Post Group 宁波city eCommerce dept. received
2016-06-14 16:49:00.0 China Post Group 宁波city eCommerce dept. customs scan
2016-06-14 16:50:00.0 leaving China Post Group 宁波city eCommerce dept.
2016-06-16 13:56:39.0 Hangzhou Transit Station export security scan
2016-06-16 15:22:28.0 Hangzhou Transit Station export customs cleared
2016-06-17 04:30:00.0 arrive Hangzhou Airport
2016-06-18 03:51:14.0 leaving Hangzhou Airport going to next airport/seaport
2016-06-18 08:00:00.0 Hangzhou departure

2. I suspect your parcel has left China to Italy. Your parcel might be in Italy Customs Office getting clear. But that, nobody knows exactly where it's at right now because the parcel has not been scan.

3. China Post Airmail Parcel Estimate Arrival Time for Italy is 2.5 to 4 weeks, you have already close to 2.5 weeks done. If after 4 weeks you have not received your parcel, try to contact seller again to explain the situation. If he does not respond then open a dispute to get your money back.

Hope this help.