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Since the device won't boot and the self-service portal isn't working, contact Surface Support directly at https://support.microsoft.com/home/contact. Have your serial number ready (it's on the original box or under the kickstand). They'll verify warranty and create the service order manually.
Alternatively, Microsoft provides in-person support for Surface through service centers. You can check locations here: Service centers for in-person support. If there's one nearby, bring the device with proof of purchase—they'll handle warranty validation and service creation directly.
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