CP2102 are pretty good ones and never let me down :-)

Is your UART connection to ESP32 working correctly? Can you see the
boot message and whatever happens next in terminal (cu / minicom)? Are
RX TX pins not swapped? Power supply okay?

Are boards generic devkits of custom hardware? ESP32 in addition to RX
TX needs two control lines Reset and Boot that will switch the chip to
bootloader / flashing mode. Most USB-to-UART use RTS/CTS lines for
that. Are you sure these lines are available on your board and
connected to the target correctly? Do you have Reset and Boot buttons
on the board so you could trigger bootloader by hand (hold Boot, press
and release Reset, device will be in bootloader upload mode, retry
esptool flashing now). You can also play with the buttons with active
terminal attached (i.e. minicom) to see if they work as expected.

Minicom serial terminal is pretty cool as it allows you to watch UART
behavior on adapter (un)plug. In minicom you can also enable/disable
hardware flow control lines (Ctrl+A O -> Serial Port Setup -> (F)
Hardware Flow Control). You can switch that easily and watch the
target behavior. If this is the problem you may want to use stty (1)
to enable/disable hardware flow control on the port.

Can you try with another board? ESP32 has fuses that may permanently
disable and/or mess up some hardware features.

--
CeDeROM, SQ7MHZ, http://www.tomek.cedro.info

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