mobile

I tried flashing CWM recovery onto my AT&T Galaxy S4 and because my phone does not connect to my computer via USB for some reason (the phone charges and my computer recognizes that there's a device in, but I cannot actually do anything with it) I flashed it with Flashify. I rebooted into recovery mode, and I got slapped with the "Unauthorized software has been detected on your phone!" message. So I tried rebooting, and I got stuck in a recovery mode bootloop with the same message. Eventually, I realized if I just go into download mode and reboot by pressing the volume down key, it doesn't try to go into recovery mode. I have already endlessly researched my USB problem, and yes, I DO have USB debugging on. ODIN recognizes that I have an external device in as well, but I haven't tried flashing anything onto my phone with it because I don't want to brick my phone because the connection to my PC is faulty. I'm using the charger that came with the device as my USB drive, so that's not faulty either. I know rooting my phone did this, and I'm pretty sure it's because I missed a step. I used this tutorial to root my phone:
[droid views dot com] /root-att-galaxy-s4-sgh-i337-android-4-4-4-kitkat-firmware-i337ucufnj4/ (I'm not allowed to post links yet, so fix the URL if you're gonna have a look)
When I flashed the I337_NC1_Stock_Kernel, my phone refused to go into download mode and I couldn't flash the I337_NJ4_Stock_Kernel as a result. I'm pretty sure that's what caused it, but I have no idea how to fix it. I'm not an expert with my phone and, despite almost soft-bricking my phone via a corrupt CWM .zip, I'm not a newbie at this either. If I could figure out how to fix this problem, I wouldn't have to worry about throwing myself into a bootloop because I can just use ODIN. I was a sitting duck before download mode rescued me, so I'd like some help as to how I can accomplish this. Any and all help is appreciated. I am 100% certain my device is the right version for that tutorial, I wouldn't try to root my phone without checking all of the simple things first.