Won't let me login to the FTB Launcher



None of the categories describe my problem so sorry.

Modpack/Launcher: FTB Infinity Evolved

Using a MacBook Pro with macOS Mojave Version 10.14.2

I’m having issues logging into my Minecraft account on the FTB profile so I can go join a server. I know my email and password are 100% correct, I used it to log into Mojang.com, minecraft.net and the regular Minecraft launcher just now.

However when I go into create a profile, put it my email and password and then hit launch on Infinity Evolved, I get this popup error:

"Invalid username or password!

  • Check your username or password. If you use OLD non-migrated account try using username instead of email.
  • You need to use paid minecraft credentials. Mojang account without paid MC won’t work."

And I get this console error:

"Invalid credentials recieved for user: (my email):
com.mojang.authlib.exceptions.InvalidCredentialsException: Invalid username format. Username must have between 4 and 16 and alphanumeric characters. Underscore is allowed."

My account is migrated so I know its uses email. I have certainly paid for Minecraft as I can get onto any server in vanilla Minecraft. I’m not sure why the its asking between 4 - 16 characters when it says Username/Email. I’m thoroughly confused and just want to play a modpack on a server with my friends.

Update: I just tried creating a profile using a friends account that he just launched with and I got the same error message, even though the email and password are correct and he was able to launch.


can you post full log please, instructions for that can be found here:


Does this suffice:



Not really, but try and delete the profile restart the launcher and re-add your account.

If it still fails, please follow the instructions on how to post the log.


Removed profile, restarted launcher, and added back profile.


Haven’t used osx in a while, and don’t have either osx or linux close by atm.

First - really make sure that you don’t get a space or other character if you copy/paste your username and/or password - then try:

  • Close launcher

  • Try and find where the files “clientToken” and “logindata” are stored, and remove those)

  • Try again, post new log if it still fails


Removed clientToken and logindata and tried again.

I keep seeing this 4-16 alphanumerical prompt in the Console, which is strange for the reason I said before but I have a feeling its why I can’t launch. It’s as though its requiring me to use a Username even though my account is Email based.

I tried using my Minecraft username in place of the email before starting this thread, and it let me launch the modpack. However I got the Invalid Session error trying to join my friends server.
Through further testing I realized It didn’t actually log me into my Minecraft account when I used the Username. I went into singleplayer and had no skin, as well as the fact I can use any Username and any password and still launch, but obviously getting the Invalid Session error as those accounts aren’t real.


any antivirus software or restrictions on folders?

If you open up the logindata file, did the launcher managed to save the new profile in that file?


Yes my Antivirus software is a program named SOPHOS. However I believe my settings it put restrictions on applications and folders and such. It just scans and prevents malicious content.

This is the Text the logindata brings up, so I assume yes it did save. All the question marks are User and folder data I assume.

¨Ìsrnet.ftb.data.UseraIa_serialZsaveMojangDataL_encryptedPasswordtLjava/lang/String;L_encryptedStoreq~L_nameq~L _[email protected][email protected]~x

Also, thanks for the time and help, if you got nothing it’s aight. My next plan is to just try a different computer entirely.


Can you show me a log when you use username instead of e-mail?


Used username.


As the launcher loaded, the logs show all the modpack loading too. Guess you only need to look at the first bit though.


Looks strange.

You could try and re-install everything - (make sure to remove all - the folders at the location of logindata as well)

Then make sure to whitelist/make exception for the game in your antivirus software, looks like something is blocking - or some left over since before you did the migration?

You could also try the Twitch app and see if that works out.
red download button: feed-the-beast.com

or try the MultiMC launcher and see if you can manage to get around the issue there.


I’ll try all these tomorrow, have too much work to do tomorrow to stay up much longer.

If all those fail I’ll let ya know and just try on a different computer, which should work (knocking on wood).

Night, and thanks for the time.