Here is a link to the Max manual which is probably very similar to the Max Carta manual:
https://my.pcloud.com/publink/show?c...PvFLQq8RyCHzTV
However, I am sure there must be a certain button combination which you could press for a given amount of time which will trigger a factory reset. You may want to contact someone like Booxtor who would likely know the combination. I would think that most of these Onyx Max devices are currently fairly similar in terms of firmware.