Reset and re-install firmware

Because my watch has a lot of issue (touch screen that no longer responds), i try to flash with this firmware:
download-agent: MTK_AllInOne_DA.bin
scatter-loading file: MT6739_Android_scatter.txt

I use flashtool, the watch is connected by USB and the pc has access to it, but flashtool do nothing.
I click on the download icon, it then becomes gray, and after, nothing.
(i can’t join picture or link with screenshot :frowning: )

can you help ?

The watch must be switched off. Prepare the flashtool as described. Click “download only”. As a final step, connect the switched off watch to the computer.

Thank you for your help.
So the watch is off
Flashtool si ready with:
“download-agent: MTK_AllInOne_DA.bin
scatter-loading file: MT6739_Android_scatter.txt”
and “download only” .
The green arrow turns gray.
I plug the watch (off), and nothing. I just can click on “stop”, no message, no action.

finally it is ok, just an issue in the MTK driver.