I have 2 shield tv's, on one market helper works, on the other it says token error. There is no fix for this I can find. If I exit my build.prop to trick the play store to think it's another device will it bork my system. I would try it myself but I upgraded to 6.0 and they haven't released the a restore image for 6.0 yet (if it borks my system, I'm down one shield tv until they release the restore image for 6.0). I'm actually surprised I couldn't find an answer for this here or in the nvidia forums.