Bluetooth LE after scan and connection, GATT server is not showing

[eric-cyber-cmd]

I'm writing the code for windows and after requesting the scan for ble devices, i save the resultin a list. From here i'm trying to connect to the device and request the gatt services. When i try to read a characteristic the program give me a null reference: don't find the gatt characteristic. So i try to read another time the gatt server and that disappeare. Jow it is possible?