To reactivate your Microsoft Rewards account and resolve issues with the fields being greyed out, you should contact Microsoft support directly. They can assist you with reactivating your account and help you regain access to your points. You can typically find support options through the Microsoft Rewards website or by signing into your Microsoft account and navigating to the support section.
Make sure to provide them with any relevant details about your account and the issue you are facing to expedite the process.
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