Possible fix
Click your name in the launcher, press Log out, then log back in
Launcher - version 1.11.2 - multiplayer - join server - error message (see above)
Linked issues
is duplicated by 56
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relates to 2
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Comments 37
Hi, I've had the same problem after my client updated. I can't access the server I play on and I have the same error message.
I play on a Mac.
17w06a is the newest Minecraft development version AKA Snapshot.
To get it, you need to enable that in the Launcher.
Seems to be related to a invalid session ID that only happens on the new launcher, hmm