How do you know you are dealing with an S1Boot issue? Look for these telltale signs:
If Flashtool failed, or you want to do it manually: s1boot fastboot driver
Upon reboot, press 7 or F7 to select . Try installing the driver again. Bootlooping Out of Fastboot Mode How do you know you are dealing with an S1Boot issue
You can also try to install the driver manually using the official file from Sony. This method works well when other options are not suitable. s1boot fastboot driver