Download Android 7.1.2 firmware for MXR Pro TV Box from here or here. Download previous firmware from here. Download Rockchip Driver Assistant v4.4 from here and download Rockchip Batch Tool v1.8 from here.
Archive: How to flash MXR Pro Firmware+Tools_7.1
Model: MXR Pro TV Box
Image file size: 822 MB
Platform: Rockchip RK3328 / RK322H
SDK version: RK30_ANDROID7.1.2-SDK-v1.00.00
FW version: 7.1.00
Boot version: 2.44
Model number: MXR PRO
Build number: rk3328_box-userdebug 7.1.2 NHG47K eng.user.20180225.101117 test-keys
Inside archive: firmware + FactoryTool-v1.43e + DriverAssitant_v4.5 + Steps
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.