I assume you did plug the dongle back in after restarting :).
To check if the computer is recognizing the device, go tot the Apple menu and select "About this Mac" and select the "System Report" button, which launches the "System Information" app.
In the report window left side, under "Hardware," select "USB".
In the right side window, under "USB Device Tree" is listed what USB devices, internal and external, are being seen by the computer. Under "Hub" you should see "RTL2838UHIDIR"
If that is there, Clicking on it will show this in the bottom pane:
RTL2838UHIDIR:
Product ID: 0x2838
Vendor ID: 0x0bda (Realtek Semiconductor Corp.)
Version: 1.00
Serial Number: 00000001
Speed: Up to 480 Mb/sec
Manufacturer: Realtek
Location ID: 0xfa130000 / 1
Current Available (mA): 1000
Current Required (mA): 500
Extra Operating Current (mA): 0
If you do not see any of the above either dongle is not working or there is a problem with the USB port.
FYI I'm using MBPro (late 2011) w El Cap 10.11.6, have been using both Gqrx and CubicSDR with the NooElec dongle. I also have the "HamItUp" prescaler.
Chuck
WV8A