Soft Bricked Verizon Galazy S3

[AC Question]

I have an older S3 that I wanted to try rooting and adding a new ROM before trying it on an active phone.

I installed the most recent TWRP and the phone immediately informed me I had unauthorized software. I was able to boot through this through home-power-vol. I then plowed forward and attempted to flash SlimRom with KingoRoot. That's where things fell apart.

I can only get into two modes on the phone now. One is the warning screen that there was a problem and that I should use the Upgrade Manager to resolve (but Upgrade Manager isn't available because the phone is bricked.) The other is download or Odin mode.

So, I have tried to follow several tutorials like this one:

www androidauthority com / galaxy-s3-i535-unbrick-soft-brick-125413/]How to restore or unbrick the Galaxy S3 I535 after being soft-bricked

I do seem to make a connection through Odin to the phone and I get a COM port and an "added" confirmation. But any file I attempt to flash fails. I am using the USB cord right out of the Samsung box and have tried several USB ports.

Any suggestions?

Thanks.