Time out when flashing ESP-01S

I try to flash an ESP-01S. For that I use a Keyestudio USB to ESP-01S which is equiped with a CH340G.

When I execute

pio run --target upload

I get

Configuring upload protocol...
AVAILABLE: espota, esptool
CURRENT: upload_protocol = esptool
Looking for upload port...
Auto-detected: /dev/ttyUSB0
Uploading .pio/build/esp01/firmware.bin
esptool.py v3.0
Serial port /dev/ttyUSB0

A fatal error occurred: Failed to connect to ESP8266: Timed out waiting for packet header
*** [upload] Error 2

My platformio.ini contains

platform = espressif8266
board = esp01_1m
framework = arduino

I am using Linux (Debian) and I have been successful in flashing other boards (seeed_xiao_esp32c3)

I am grateful for any suggestions.

Did you make sure to flip the switch into the “UART Download” position and unplug & replug the board so that the ESP8266 is for sure in bootloader mode?



I used the Uart-Download-Mode, but probably without replugging.
Indeed this helped!
Thank you!