I am using Visual Micro with Arduino 1.6.7 & Atmel Studio 7.
Sparkfun AVR boards are installed under the Arduino IDE, but don't appear on the list of boards under Visual Micro/Atmel Studio 7.  
I have configured the board manager URL, and "Sparkfun AVR boards" appears on the boards installer list. When I run the installer, it acts like it's working and adds Sparkfun AVR boards to the "installed" list under the board manager. But Sparkfun AVR boards don't appear on the list of available boards in Visual Micro. If  I restart or rescan , Sparkfun AVR boards vanish from the board manager "installed" list and re-appear as available to be installed.  

I tried installing the boards within the board manager from a .zip file, which also failed (unable to extract to the required directory; of course the unzipped folder is already in the correct location, because it's installed for Arduino IDE).

Thanks.

Thanks for the prompt response.

"SF32u4_boards-master.zip" downloaded from https://www.sparkfun.com/products/12587.

I fixed the problem (Well, found a workaround):
Removed "Sparkfun AVR boards" from Arduino 1.6.7 board manager, then manually installed the board files (i.e. unzipped and copied the "sparkfun" folder to Arduino/hardware folder.)

I tried installing from the .zip file using the Atmel Studio/Visual Micro board manager, not the Arduino board manager ("install new hardware from zip" is an option at the bottom of the Board Manager tab of Visual Micro explorer).