Can you try pressing ctrl+shift+f2 from within Kitty and then adding font_size 20.0
? That will make sure you are editing the same config file Kitty is using.
If that doesn’t work, I’d try deleting the config and then try again. Kitty should automatically create a new config.
Since nobody else said it: make sure you have backups of any data you don’t want to lose. It’s really easy to accidentally partition any connected drive and wipe your data on it. (Learned it the hard way, but at least I had backups.)