Download Android Lollipop 5.1.1 stock firmware for Rupa Mini MX9 TV Box from here or from here. BTW, you can now buy Rupa Mini MX9 TV Box from Gearbest for only $28.64 with free shipping world wide.
Model： Rupa Mini MX9 TV Box
Image file size: 562 MB
Platform: Rockchip RK31229 / RK322A
Model number: MINI MX9
Boot version: 2.31
FW version: 5.0.00
Build number: rk322x_box-userdebug 5.1.1 LMY49F eng.foxluo.20170208.152823 test-keys
SDK version: RK30_ANDROID5.1.1-SDK-v1.00.00
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.