Download Android Nougat 7.1.2 firmware for Tanix TX28 TV Box from here, here or here. Download from here the OTA firmware version. Download Rockchip Driver Assistant v4.4 from here and download Rockchip Batch Tool v1.8 from here.
Archive: TANIX TX28 20180626
Archive size: 706 MB
Platform: Rockchip RK3328 / RK322H
Image name: TANIX TX28 20180626.img
FW version: 7.1.00
Boot version: 2.44
Build number: rk3328_box-userdebug 7.1.2 NHG47K eng.zheng.20180626.101551 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.