I rooted my Nexus 7 2012 Wi-Fi running 5.1.1. yesterday (worked great). I tried to flash a ROM for Kitkat (KTU84P) and it stopped booting. I've tried all the usual ways to hold down the Power, Vol +, Vol -, and both volume buttons. I can cycle through the START, RESTART BOOTLOADER, POWER OFF, AND RECOVERY MODE options but NONE of them work except OFF. RECOVERY MODE shows BOOTING FAILED when I push the power button. NOTE: I can't load any files to the Nexus 7 because after it bricked, the USB cable doesn't even recognize the tablet and there's no way to transfer files or see what's on the Nexus. I'm guessing I'm hosed, but thought I'd ask to see if there's any way to fix the USB issue (worked before it got bricked) so I can download files and fix it.
You may easily fix this and unbrick it using the stock Google Android Factory Image.
Step-1: Download the latest Android Factory Image file for Nexus 7 from here
Step-2: Extract (Unzip) the content from the downloaded file and save it in a folder on the computer.
Step-3: Download USB drivers from here
Step-4: Boot the tablet into Fastboot mode. For this press and hold
Volume Down and Power buttons together. Release all the buttons when the Fastboot screen appears. You should see the Start option listed in the upper part of the screen.
Step-5: Connect the Nexus 7 to the computer using USB cable.
Step-6: Navigate to the Factory image folder created in step-2.
For Windows: double click flash-all.bat file.
For Mac or, LINUX users launch flash-all.sh file
Step-7: Wait for some time until the installation is completed
Step-8: When the installation process is completed, press Volume Up until the Start next in the Fastboot Mode changes to Recovery mode then press Power button to boot into Recovery.
Step-9: Select wipe data/factory reset and confirm the process
Step-10: When the Factory Reset is completed, select reboot system now and wait until the Nexus 7 boots into stock Android
If you install fastboot and adb drivers onto your computer, it shouldn't matter if your tablet is in bootloader, failed to get into recovery (usually because while trying to install a ROM, most will use a custom recovery like TWRP, and if not installed properly, it is only a one use recovery, untill the OS is Booted then its gone.) all you need is ADB and fastboot on your computer, then flash a new rom, or a stock rom through cmd.