Nice work getting up and running, it looks like code is compiling ok using Platformio
I don’t recognise that USB programmer. What are you using?
I would recomend you erase the flash before uploading using:
$ esptool.py erase_flash
If you don’t need to change the FW you could download the FW and SPIFFS from the emonesp github releases page then upload both in one go using:
$ esptool.py write_flash 0x000000 firmware.bin 0x300000 spiffs.bin
You will need to install esptool: