Null 23 is not installed

You can't install null without twrp

Sent from my GT-I9505 using XDA Premium 4 mobile app

I have the same problem too.
but now I have successfully install it.
Please do this trick :

1. open command window and run : adb devices. (make sure your gear was connected, and don't close this window)
2. in the same time run cydia impactor, when showing "# drop SuperSU su to /system/xbin/su" click start.
3. open software wondershare mobile go or other software to copy the rom ( null_23.zip) to sdcard. after that you may close this software.
4. open software Odin then located and choose your "null_03_TWRP2.7.tar.md5" file. Remember to uncheck Auto Reboot. the go with button Start. Wait until the process complete.
5. When you sure the process has completed, back to command window and type : adb reboot recovery. The gear will reboot with recovery mode and goto install rom.

Now I have Custom ROM ( Null_23 ) in myGear. And I can using with iphone 5 ( only for call/Answer phone )

I hope this can help you to install the new custom rom Null_23.zip.