Single player worlds and branch off servers

I am unable to load single player worlds. I can get onto Minecraft servers but am unable to reach any other servers from the lobby. Also, when I log on, everyone has the default Steve and Alex skin. When checking logs and startup, there is nothing wrong besides the warning "Skipping bad option: lastServer:" but I already read on that and it shouldn't affect anything. I have looked for a couple days now but I can't find the issue. Sorry if there is a fix and I can't find it but everything looks normal and I can't figure out what's wrong.