Which Konform version and operating system are you using? Can you log in to itch.io in another browser on the same device?
I have had this issue on every version of Konform Browser I have tried. So far I am at the current version.I am on Linux Mint and LibreWolf and Zen both allow me to log in, but for some reason no matter what I do in the settings Konform won't let me log in.
