device not yet registered

hi everyone
i've got a problem with my g2 d80220c when i tried to update from kitkat to lollipop, when i searchh for an update it says your device is not yet registered , and when i use lg support tool the application stops working .
some say i've got to get an at&t simcar but i can't get when caus am not in the us .
please help me fix that given that i dont want to root or mess up my phone and thnx:)