If your plug appears to have died;
Do NOT break the anti tamper seal, yet.
Email or phone your supplier, detailing the problem, be polite!
You should get an RMA number or similar and return the device. Try to get a prepaid return parcel label from the supplier, the postage cost of returning a defective item is normally paid by the consumer, but its worth trying to get the supplier to pay!
If the plug failed within a few days, of delivery, insist on a complete replacement device. Do not accept just a replacement power supply you have to fit yourself. The reason is,
unless you are a qualified electrical engineer, it is risky to be sent a replacement power supply and to fit it yourself. It is not a consumer replaceable part. It raises questions regarding your own safety and also third party liability if the power supply you installed at a later date catches fire and burns down your house and your neighbour's house!
If your device has a EU approval mark, then if you are in the EU, you should have a TWO year mandatory warranty for electronic devices against failure due to manufacturer defects! Although it is EU law, it has not been properly described and promoted, and not many people are aware of it.
Always approach your supplier for redress in the first case.
I have no idea about consumer law outside the EU, You will have to find out the applicable consumer law in your own country.
Also, I have no idea of the law where the customer resides in one country and the supplier in another continent!, Which countries laws are superior and have to be observed?
Be patient, do not bad mouth your supplier in public places, it could be expensive!
as usual YMMV, IANAL