Failed to Authenticate error only on Forge

[Rhiku]

Hi, I've been having this issue for the past 3 days trying to fix it, for some reason I'm having issues with authenticating but it only happens when using forge. Whenever I try to join any server on forge it gives a "Failed to login: the authentication servers are currently not reachable" error. It also applies for singleplayer worlds, my skin is always steve since it can't authenticate. Any help on this issue would be greatly appreciated as I feel like I've tried literally everything I possibly can. Just so that you know, I've already checked my hosts file to verify that it's not blocking any minecraft connections, as well as various other fixes that haven't ended up resolving the issue. The only way I've found to get around the error is to use a VPN.

[ChampionAsh5357]

Would you mind showing the debug.log with the error itself? Although it may not have the answer, it could give us insight into where the process stopped working as this issue seems highly inconsistent between users.

[Rhiku]

Didn't exactly know how to access the debug.log, managed to find it in the curseforge settings though. Here's the log from me loading the game, trying to join a server, then closing. Just uploaded the log to mediafire since I couldn't fit it into a pastebin or anything.

https://www.mediafire.com/file/8snyu6be0e6w4lf/debug.log/file

[ChampionAsh5357]

If you can, use a gist instead since that supports up to 100MBs. Not to be rude, but people are not going to download files off the internet from people they don't know.

[ChampionAsh5357]

So, after talking it over with somebody who knows more about connection protocols, it is likely that you have an improperly configured firewall that only blocking traffic in one direction instead of both as it is trying to connect with ipv6. You either need to block both directions or neither.

[Rhiku]

Sorry about that, just thought mediafire was well known enough since I've been using it for years. Kind of my go-to file sharing site. Also cause I didn't know how to use github, but I think I figured it out. Here's the link.

https://gist.github.com/Rhikuu/676fb1519b172807bdff5bcd77c23e12

Also just got your new reply, what exactly would be blocked? I've already allowed the 25565 port through incoming and outgoing connections through my firewall for minecraft.

[ChampionAsh5357]

On 12/30/2022 at 1:36 PM, Rhiku said:

Also just got your new reply, what exactly would be blocked? I've already allowed the 25565 port through incoming and outgoing connections through my firewall for minecraft.

It's not a firewall thing, it has to do with what you are using to connect with your ip address, either ipv4 or ipv6. From what I've been told, it's likely that one direction is blocking the ipv6 traffic, using ipv4 instead preventing the connection from occurring. As such, you need to change the settings for your device or router to either block ipv6 traffic incoming and outgoing, or don't block either.

[Rhiku]

Would you happen to be able to explain how to do that? I haven't heard of that ever being an issue till now.

[Rhiku]

Nevermind that was actually very easy to figure out, thanks so much! That actually seemed to fix the issue. I joined the server with no problem this time.

[Rhiku]

I am a little confused though, why is this issue only on forge? Is there something forge changes that would cause such an issue?

[ChampionAsh5357]

19 hours ago, Rhiku said:

I am a little confused though, why is this issue only on forge? Is there something forge changes that would cause such an issue?

A PR was made to Forge which supports ipv6; vanilla meanwhile does not have full support for ipv6 and there is no mixin in base fabric which supports it as well.

[Slidebrain]

On 1/1/2023 at 7:27 PM, Rhiku said:

Nevermind that was actually very easy to figure out, thanks so much! That actually seemed to fix the issue. I joined the server with no problem this time.

Hey there, now i gotta ask since i'm in the same situation, how did you fix it in the end?

[Rhiku]

2 hours ago, Slidebrain said:

Hey there, now i gotta ask since i'm in the same situation, how did you fix it in the end?

You just have to disable ipv6 in your network adapter settings.

[Peekofwar]

This is the second time I've had issues connecting to a modded Minecraft server. The first time was my private ATM8 server, which was fine for a while before it kept saying authentication servers were down. I assumed this was caused by something in the ATM8 modpack, and effectively killed that private server.

The second time was my main modded server, which neither me or my friend has had any problems with until today when it started saying the authentication servers were down. As a troubleshooting step, I restarted the server, but the error still appeared. My friend mentioned that he was able to connect with no issues to my private vanilla server (hosted on the same machine as my modded server) which suggested to me this could be an issue with Forge. This also reminded me of the ATM8 server issue.

So I searched Google for "Forge 1.20.1 unable to authenticate" and found this forum post. Noticed that someone suggested disabling IPv6 in the network adapter settings worked for them. I then proceeded to disable IPv6 on my server's Ethernet adapter (and also wondered why the WIFI adapter was enabled since I've previously disabled that TWICE), and without even needing to restart the dedicated server or the machine itself, I was able to successfully connect with my main computer (which is on the same local network).

In short, disabling IPv6 in the network adapter settings fixed the issue.

[FinnT730]

@Peekofwar It might be that you just need to close the game, and log out of the launcher and then back in again. Might be very well that the Microsoft Servers could not verify you on time, and you got that message.