Download Android Nougat 8.0 firmware for A5X Max+ 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: 2768333 A5X MAX+ TV box ROM firmware pack
Archive size: 785 MB
Model: A5X Max+ TV Box
Platform: Rockchip RK3328 / RK322H
Image name: mxq_rk3328_d4_8.1_IT6334_a5xmax+_20181012_r1.img
FW version: 8.0.00
Boot version: 2.46
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.