With Bonjour service enabled on your computer, you can discover nearby AirDroid users and share files with them.
How to start Bonjour Service?
Go to Control Panel > System and Security > Administrative Tools > Services or simply go to this path: Control Panel\System and Security\Administrative Tools:
Find Bonjour Service and double click it, select Automatic and click OK to confirm:
Please make sure the Service status should be Started, if it shows Stopped, please click Start to start the service: