Download Android 7.1.1 stock firmware SD card version for MECOOL M8S Pro L TV Box from here and here. Download Android 7.1.1 stock firmware PC version for MECOOL M8S Pro L TV Box from here and here. Download previous version from here.
Archive: MECOOL M8S PRO L-20180803 / MECOOL M8S PRO L-ota-20180803
Model: MECOOL M8S Pro L TV Box 3GB RAM / 32GB ROM
Image file size: 578 MB / 638 MB
Platform: Amlogic S912
Image: MECOOL M8S PRO L-20180803.img / MECOOL M8S PRO L-ota-20180803.zip
Build number: M8S PRO L-userdebug 7.1.2 NHG47L 20180803.173707.V0213 / Amlogic/q20x/q20x:7.1.2/NHG47L/20180803.173707.V0213:userdebug/
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.