Because after factory reset,the activation file was deleted. Need to re-activate.You need to contact the manufacturer to check the activation code and provide the serial number of the device.(android 7 path:setting>about tablet>statu)Please download the activation software and guide here:https://terabox.com/s/1-lKpBJFGX0KXJTDDloVXKA orhttps://mega.nz/folder/F6QXAbBS#_C80gcTE6HV5xde1r0Wupw