Atmega8 with STK500 ISP

Hm if it goes to the verification then the programming part must have been done. But seems like the chip wasn’t erased before.

Can you add

upload_flags = -e

to the platformio.ini, then Build the project once and then execute a “Verbose Upload” (Project tasks → Default → Advanced → Verbose Upload All" and post the log here, starting from Use manually specified: COM5?