Ok have you tried going into the bootloader and getting into recovery?
If you get a android with a red triangle just press Vol-Up and power then clear the cache then do a factory reset and then reboot and see what happens.
If after the reboot your still in the same boats as you was before the apx flash then i think it could be due to a messed up partition somewhere (bad block on emmc) i am still looking for other ways of recovering the devices that have bricked but Nvidia has decided not to reply to my messages (Thats the mobile team support for ya!)
Retired Mobile: HTC Wildfire (Buzz) Hboot: 1.02.000 (Superversion)
SecureFlag: On (Was Off'd with XTC Clip)
Rom: None Blanked for Testing Roms!!!!!!!!!
Boot Manager: Full Version Paid and Worth It!
New Mobile: HTC Desire HD
SecureFlag: Off Via XTC Clip (I love my clip its so nice!)
Rom: Pacman Rom
Advent Nvidia Note 7 Tegra 4
Recovery: CWM 184.108.40.206