Factorio Forums

Reproduction instructions:
- Fresh install of 15.1 (in my case, running from downloaded zip file)
- At start up prompt to log in Factorio account, log in using email address as user name. Login is accepted
- Poke through the Options menu. Go to Other settings
- Note that email address is displayed for both Factorio user name, and logged in as
- Try to enable experimental updates and click Back
- Receive error that username contains invalid characters
- Click the log out button
- Log in using email address again
- Note that the non-email user name is now displayed for Factorio user name and logged in as
- Enable experimental updates, and click back - no error message

Someone on Steam had a similar issue: http://steamcommunity.com/app/427520/di ... 9028021467

His username (the one registered on the website) contains an apostrophe (') but he is unable to set it in Options --> Other since it is restricted to letters, numbers and ._- characters. If you leave the field blank, start a new multiplayer game and get prompted for the username then you can use the apostrophe.

I suggest the devs check all usernames and allow those characters found to be used in Options --> Other.

This issue was fixed in 0.15.12 by this change:

Fixed logging in with email in updater set your username to your email. more

Note: I suspect the issue described by daniel34 may still exist, I don't have a username with a ' to check it