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From the document - DevicePairingResultStatus Enum, the OperationAlreadyInProgress state means The device object is already attempting to pair or unpair. When the pairing process is not finished and the pairing method is called again, this result will be returned.
Please do not call the pairing method multiple times in a short time. Make sure the target device's pairing process is finished before calling the pairing method again.
Thank you.