CC2640R2F: CC2640R2F Central mode: GATT_WriteCharValue return 0x16

Part Number:CC2640R2F

Hi all, I have troubles with my CC240R2F in BLE Central mode. I have modified "simple_central" project for communicating with a BLE Lamp (peripheral). In my code (attached below) it works scan, connection, and service/characteristic discovery, but when I try to enable notification on a specific characteristic and write a value on it (a simple string as lamp documentation for turn on the lamp), the GATT_WriteCharValue function return always 0x16 and the lamp doesn't turn on. What's wrong with my code? How can I resolve this? 

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