I have this issue too, but rebooting hasn't helped.
I have a MacBook Pro 13" 2013 using Yosemite official release and I wanted to test AirDrop using my mother's iPad Air which is on iOS 8.1. The Mac could see and send files to the iPad immediately, no problem. But the iPad doesn't see the Mac.
I've tried:
- rebooting both devices several times
- tested both 'contacts only' and 'everyone' settings in all combinations
- logged out of and back in to iCloud on both devices
- logged in as both my @gmail and @me addresses in iCloud on the Mac
- had mobile LTE on and off for the iPad, with internet sharing on and off
- internet connection on and off going into the MBP
- looked for all possible updates
- tested sharing from various apps on the iPad
- firewall on and off on the Mac
- logged in as my mother on the Mac, so that both devices were logged in on the same iCloud account
I just can't get the iPad to see the Mac for AirDrop.
Surely at this point it must be a bug?