I´m playing Stoneblock 3 with the FTB Launcher and i can´t use Reauth or Oauth.
On Reauth there was not even an error it just did not let me login and join servers.
Oauth at least gave me this. But no clue at all how to fix this one

Try updating to the latest version of oauth

does not work.
newest version auf Reauth does not work at all( no error no nothing the game just closes)

latest.log

Looks like an internet related issue if neither are working. Without knowing your exact setup I can't really help.