Fastboot or recovery no longer work

Hello, I flashed a GSI ROM onto my Hi 9 Pro (using PHH Treble v123 worked, but all the hardware buttons disappeared. I tried to jump to the Android 10 versions unsuccessfully). Now the system no longer is able to boot normally, to enter fastboot, or recovery. If you press volume and power, then select the option, the screen turns black.

I don’t really understand how to operate SPFlashtool. There are references to scatter files which I don’t know where to find.

Any ideas?

Here is firmware
Hi9 Pro Android Firmware download: (before serial number 201901 )
Hi9 Pro Android Firmware download: ( after serial number 201901 )

Scatter file you can find in folder with firmware

spoiler(for example)

In flashtool choose “firmware upgrade”, don’t choose “format+download” this will delete configuration file and you will have problems with sim and wifi.