Don't waste time, if the hardware has locked oem and that oem unlock is greyed out, you cannot unlock it. You'll need a specific code or unlocking tool from hardware manufacturer to unlock any tablet that has the boatloader locked. there is no other way around it. only a few tablets can load new firmware that was not original. nexus 7 you can load android on it. most tablets you need manufacturers tool to communicate with the software in the chip level. you can remove the chip and put chip in it but that is too much work the tablet is stuck with the OEM software. and you cannot even upgrade it. contact the manufacturer. only pixel cell phones or some cell phones you can unlock oem. these cell phones are subsidize by the cell phone company and you can only use the cell phone on their network. that is the reason you cannot unlock it from business perspective. you subscribe 5 year phone plan and cell phone is free promotions. What you have wrong tech advice telling people you can unlock it when you cannot.
