were you on COC5 update before flashing?
i am just trying to figure out whats going on... it seems like you are stuck on a locked bootloader, and since there is no new Odin flashable bootloader released yet you have to wait for a new release...
besides that it seems like you have done almost all appropriate steps... here other steps you can try:
1. Flash with a pit file (attached within this post)
2. Try this pre-rooted firmware:
androidfilehost.com - N910AUCU1COC4_Rooted.tar.md5
3. Flashing custom recovery is not an option for you since its bootloader is locked and only developer edition phones can be flashed with custom recovery...
4. You can try this insecure boot, if it works you may flash to stock:
androidfilehost.com - insecure_boot.img.tar