Fatal error was starting Putty after having saved settings

A few days ago, I updated my Putty configuration to set the default font-size to 12; no more 10.

Today, when starting Putty — whichever server I wanted to connect to — I got the No supported authentication methods available error, followed, in my case, by (server sent: publickey, gssapi-keyex, gssapi-with-mic, keyboard-interactive).

I only understood the origin of the problem by looking at the window caption: Putty was trying to connect to a server other than the one I wanted. Why? And, ah, ok, the last time I modified my settings I was working on that server so, the solution should come from: how can I reset my Putty settings?

The solution has been provided by @makurison on https://stackoverflow.com/questions/57072011/delete-putty-default-settings-modification-to-original.

Simply start regedit.exe, search for the key Computer\HKEY_CURRENT_USER\SOFTWARE\SimonTatham\PuTTY\Sessions and, there, remove the entry called Default%20Settings.

While you're at it: KeePass - Overriding the URL field shows how to launch a PuTTY session straight from a KeePass entry, credentials included — and Windows Terminal - Adding a SSH profile does the same without PuTTY at all.