Download Android 9.0 stock firmware for Tanix TX6 TV Box from here or here. Download previous firmware from here. Download Android Nougat 7.0 stock firmware PC version for Tanix TX6 TV Box from here. Flash it from PC using LiveSuit v1.11 or from SD card using PhoenixCard v3.09.
Archive name: Tanix_H6_4Gddr_8822bs_20190228
Archive file size: 718 MB
Platform: Allwinner H6
OS: Android Android 9.0 stock
Caution Please do not update firmware unless you know what you are doing, you really want it or it is absolutely necessary. Firmware updates may occasionally have bad results, like bricking your device, temporarily or permanently. The firmware update process is done entirely at your own risk. Before attempting to update the firmware, back up your data.