iOS 9.3.1 / OS X 10.11.14: Laptop doesn't show up in Airdrop locations on phone
There are number of methods to get it working so try them out one by one what works for you.


Try creating new user in mac and test airdrop with 
  -icloud signed out
  -icloud signed in
Reset PRAM ans SMC
Try switching on/off bluetooth/wifi on both the devices.
Network reset in iPhone.
Test the same machines in different wifi at different location sometimes it is an issue of wifi router also. // This has happened with me.
Check firewall in mac and disable it temporarily.
Try without connecting to any network on both the devices i.e. forget wifi on both devices but enable wifi/bluetooth on both.
Try it in Safe mode.
If you have another mac available then try to airdrop with mac to mac.


Happy airdrop debugging :P