I've been looking awhile and so far all the bootloop/soft brick threads I've seen advise using fastboot, adb, or recovery mode. Well, none of those are available in this case. Here's the story:
I got a Nexus 7 2nd gen, used Wug's toolkit to unlock and root it, then tried flashing CM11. The latest nightly build was full of bugs, so I tried 10.2. That didn't work at all, so I tried the latest snapshot (m4). Now the tablet won't get past the Google screen.
Adb recognizes it, but says it's "unauthorized." Can't enable USB debugging for obvious reasons.
Fastboot doesn't recognize it at all.
Recovery mode isn't working. Holding the volume buttons and trying to use adb both don't work.
Thanks in advance.