flashing failure for note 4 SM-910F with odin need some help

hi everyone i'm new to this forum so bare with me please.
i recently bought a galaxy note 4 sm-910F and it was rooted, i wanted to get rid of the root in order to get the updates for android (because the phone is running kit kat) but i couldn't after doing some research i found that i have to flash the stock firmware of lollipop for my model using Odin. i checked the usb debugging and followed the instructions but when i press start in oddin here's what comes :
<OSM> Enter CS for MD5..
<OSM> Binary Check MD5.. Do not unplug the cable..
<OSM> Please wait..
<OSM> Checking MD5 finished Sucessfully..
<OSM> Leave CS..
<ID:0/004> Added!!
<ID:0/004> Odin engine v(ID:3.1100)..
<ID:0/004> File analysis..
<ID:0/004> SetupConnection..
<ID:0/004> Initialzation..
<ID:0/004> Get PIT for mapping..
<ID:0/004> Firmware update start..
<ID:0/004> SingleDownload.
<ID:0/004> aboot.mbn
<ID:0/004> NAND Write Start!!
<ID:0/004> sbl1.mbn
<ID:0/004> rpm.mbn
<ID:0/004> FAIL! (Auth)
<ID:0/004>
<ID:0/004> Complete(Write) operation failed.
<OSM> All threads completed. (succeed 0 / failed 1)

please help me i want to get rid of this root . thank you very much in advance