Add Wifi to SKR Pro step by step helped me flash my ESP01s. V1E ESP01s came preflashed.
Had trouble connecting to the device initially, used “Wifi Analyzer” app on my phone to identify which wifi access points/devices were fighting with the ESP01s, temporarily turned some of those off until I could connect and tweak the ESP01s settings to join main network. Which didn’t work out great either, connection to nearest access point seemed like too much of a struggle for ESP01S, I don’t want to buy more access points right now, so finally ended up running ESP01 in AP mode and sitting tablet/laptop close by when connecting, whipping out “Wifi Analyzer” if/when experiencing connectivity issues.
ESP3D has a reset settings on boot up mode that involves connecting some pins, I forget exactly, it’s buried in the ESP3D’s docs/github. Good luck!