Good morning everyone, We have been trying to do a firmware upgrade on our Zt-280,C-91 tablet with no success. It seems we have a very odd model number. I am Enclosing a Photo of the model # tag. Anyone recognize it? BTW..We purchased this tablet from Zenithink US, in Texas. They are no help. We've Emailed them 3 times, and no return Emails from them! Please don't believe their website, where "we service what we sell" baloney. Thank you!