How to set the Device status is "Online"

Hi ,
I could see my device status is ‘Offline’ while run the command “adb devices” , Can someone suggest how to make it ‘online’ (Android device)


@Mohan1, Can you run the command “adb kill-server” and then “adb devices” again to see if it works?

@huynguyen I ran but it not work. How can I do?
I set USB to: Transfer files . Is it right?
Please help me!