Microsoft publishes a Limited Hardware Warranty page for Bulgaria that applies to Surface devices, Xbox and PC accessories in Bulgaria. That doesn’t prove the repair backend can ship from Bulgaria, but nothing suggests the country is excluded.
Update the warranty with proof of purchase. Microsoft has a process for this when the device warranty does not match your proof of purchase. Upload the invoice, which can also fix a wrong registration region.
Use a private browser window with extensions off, and enter the address in Latin characters, with the phone number as +359 followed by the number.
Under EU consumer law, the retailer is legally responsible for defects for at least two years from delivery, whatever Microsoft’s own process does. Contact the seller in writing. Microsoft’s own page also says that in some countries and regions there are in-person service options, so check whether an authorized service provider exists near you.
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