Tag not monitored by Microsoft.
Visit:
support.microsoft.com/devices and look up the controller by serial number there rather than relying on it appearing under your account's device list.
The general path for Surface/Xbox service creation is: sign in at account.microsoft.com/devices → "Select device for service" → choose the device → follow the service request flow. If the controller genuinely won't populate there, the fallback is Microsoft support's contact page rather than the self-service portal — you may need a live agent to manually create the service order tied to your account and the controller's serial/proof of purchase.
Since the automated flow isn't recognizing the device, an agent will likely need to verify warranty manually using the serial number and receipt/order info rather than pulling it from an existing device record.
The "unable to process your request for a callback" error is usually a temporary backend/queue issue on Microsoft's side, not something tied to your account specifically — worth trying again in a few hours or the next day or trying chat support again since that's a separate queue from callback.
#Is this a known issue? Yes — functionally, most Xbox controllers aren't fully supported by the Devices self-registration flow, so a "successful" registration not resulting in a listed device is a known limitation rather than an isolated bug on your account.
#Manual registration/service creation workaround? There's no user-facing manual override — the reliable path is going through a live Microsoft support agent who can create the service order against the serial number and your proof of purchase even though it won't show in your Devices list.