It is important that the wiring has been implemented correctly. Check if every wire has been connected in the right position (see the image below).
If the problem persists we suggest you to check the origin of every wire: sometimes the wires color doesn’t reflect the standard wiring so even if it seems that the wiring is correct it may be that the wire itself leads to the wrong connection.
If you are not familiar with electrical work, we recommend you to contact an electrician.