Also use the right flash mapping that is default existing on platformio. Time to remove arduino ide and upgrade to pio! I made easy vanity address generator and that is working as Vue js PWA Net application on github-pages right here: The conversion charge of Vanity (VNY) to ETH was https://stayindirectory.com/listings12703427/%E9%92%B1%E5%8C%85%E9%9D%93%E5%8F%B7%E5%9C%B0%E5%9D%80%E7%94%9F%E6%88%90-for-dummies