Folks should be connecting to the shell server with the address shell.sonic.net. "sh.sonic.net" will get there too, but that is the canonical name of the host -- if we change hostnames in the future, that one might cease to work!
The message about incomplete authentication is a by product of supporting Google two-factor authentication. It can be safely ignored.
I'll look at the sshfs stuff when I get to a computer. I suspect when your multiple sessions were cleared your sshfs processes were also killed off, leaving the server in a state where it will report "transport endpoint is not connected" for those directories.
Logged in fine last night, Started a screen session with several mutt windows. Did stuff, but had to go. I disconnected by closing the Putty window (F4-Alt - a habit). Is it important now to use exit or create an alias for "exit"? Never mattered before.... because today I'm having the same login problem behavior from Putty.
Just tried logging in 2x, and the Putty window closes after I enter my passphrase again.
It acknowledges the correct passphrase with that familiar 'further authentication required' then POOF -- puTTY is gone.