Most of the random launcher issues are cleared up now, but I'm still seeing a couple users have trouble with login. The new launcher v6 includes a bit more debug logging that will hopefully help us pinpoint that.
You should be updated automatically. To check if you are running the latest launcher, your log file will say "Local launcher version:6". If it indicates a lower number, then right click 8BitMMO in steam -> files -> verify integrity of game cache, which should force an update.
If launching via Steam doesn't work, try the logger batch file.