Download Android 7.1.2 stock firmware for Tanix TX9S TV Box from here or here. Download Android 9 firmware from here. Download Amlogic USB Burning Tool v2.0.8 from here or download Amlogic Burn_Card_Maker v2.0.2 from here.
Model: Tanix TX9S TV Box
Image file size: 789 MB
Platform: Amlogic S912
Image name: Tanix-TX9S-20191212.img
Build number: q201-userdebug 7.1.2 NHG47L 20191212 test-keys
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.