@MojangSupport Hello, whenever I try joining my friend's realm I get this error. Everything worked yesterday but when I tried to log in 12h later, it always showed this message. It's been another 12 hours now and it still hasn't been fixed...

I still have the same error. Maybe it's a problem regarding my ISP because the same thing happens on a different system + different account aswell. No idea how to fix this though @MojangSupport

If you have any third-party software or launchers such as MCLeaks installed, make sure to uninstall and run an Antivirus sweep for malware so that nothing can interfere with the authentication servers. Let us know if you find anything or you're still running into trouble! ^AM

@MojangSupport I've tried to spot the issue and it seems to be my ISP. I've written about it on the bug forums. Here's a screenshot of what I've tried if you don't mind looking at it.