Phone stuck on boot animation, won't sideload topic

I unrooted phone to update to Android 5.0.1
Wiped data & cache and tried to reboot but phone won't load past boot animation
I have tried everything I can find online. Phone appears in Device Manager as Android Device, but does not connect to PC when in command prompt.
adb devices shows no devices
when I start phone in fastboot, then recovery mode, I can select to install a file via ADB
when I choose this, and run adb devices in command prompt, it then shows a sideload device
but when I go to load a file, it gives me the same error every time:
E:footer is wrong
E:signature verification failed

Is there anything I can do? Please help! Thanks.