Nexus 7 won't boot past "Google" screen

So, for a long time, my Nexus 7 never worked, because the charging port was too loose. So I decided to order one. It came in the mail today. Installation was easy. It started charging, but no charging icon appeared. The only thing that happend was the screen back light turning on slightly. So I let it charge more. The Nexus turned on!... But got stuck on the Google screen. So I try and use fastboot and starting it from there. "Boot failed". So, maybe no OS? Try using ADB to flash stock android onto the device. "Failed (Bootloader locked)". Ok, ill just unlock the bootloader. "Unlock failed (unknown error)" . Maybe flashing a new recovery will work? Nope, has to be unlocked. So far, nothing has worked. Spent 2 hours trying to flash, unlock and factory reset, and nothing but "failed" has come up. The device can't even go into recovery mode. When connected to adb, The list of adb devices is blank. It knows the device is connected, but it doesn't show the name or model.
Anyone know what to do?? (I have never tried to flash anything previous from today on this tablet.)