New model just received will not flash even through USB

[seamaster101]

Hi I just received 4 thermometers


I tried OTA first but it fails. Then I read that it should be flushed through USB because there is signing going on.
Then I tried through USB upgrade, but that did not work either. I am using 3.3 V USB to UART device.
The new board has a chip on the top, which I don’t see on the pictures you published.

I presumed the connection points are the same and tried it with USB connection as you recommend, but unfortunately did not want to flash. Do you have any recommendations? You also mentioned to increase the reset time and I’m not sure how to do that.
One other thing, my board does not have RTS it has DTR and STC only. Which one of those I should be using to the RST connection on the thermometer?