TL;DR If your computer is connected to Ethernet as well as Wifi, take the Ethernet cable out !

My Macbook just would not transfer files to my iPad or iPhone. Sometimes it would 'see' the device, but transfer would time-out and fail.

I had tried all the suggested solutions:

  • Flight mode is Off
  • Both devices on the same Wifi network with Bluetooth enabled
  • OS up-to-date
  • Discovery mode is set to Everyone or 'Contacts only' if the devices have each other as contacts
  • Turned Wifi and Bluetooth off and on
  • Open Airdrop folder on the Macbook
  • Reset Nework settings
  • Hard reset.

In other words: 'The Works', matter what I tried, nothing worked.
At my desk I tend to also connect the Ethernet cable even if Wifi is active and guess what:

Unplugging the Ethernet suddenly made Airdrop work!

Hope this helps someone