Please assist. Updated to 10.11.4 and now airdrop doesn't work.

Try the troubleshooting steps here >> http://www.imore.com/how-to-fix-airdrop-iphone-ipad

Boot into Safe Mode, then boot normally. Safe Mode startup is slower than a standard startup.

IReset the SMC

Reset the PRAM

1. Restart the computer and after the chime press the COMMAND and R keys until the Progress bar appears.
2. When the Utilities Menu appears select Disk Utility, then press the Continue button. After Disk Utility has started select the indented Macintosh HD entry from the side list. Click on the First Aid tab in the toolbar. Wait until the Done button appears, then quit Disk Utility. Select Restart from the Apple menu.
3. Download and Reinstall OS X El Capitan 10.11.3 Combo Update.

You'll have to recreate all Bluetooth pairings after taking this step.

Back up all data.

Triple-click anywhere in the line below on this page to select it:

/Library/Preferences/com.apple.Bluetooth.plist

Right-click or control-click the highlighted line and select

Services ▹ Reveal in Finder (or just Reveal)

from the contextual menu.* A folder should open with an item selected. Move the selected item to the Trash. You may be prompted for your administrator login password. Restart the computer and empty the Trash.

*If you don't see the contextual menu item, copy the selected text to the Clipboard by pressing the key combination command-C. In the Finder, select

Go ▹ Go to Folder...

from the menu bar and paste into the box that opens by pressing command-V. You may not see what you pasted because a line break is included. Press return.