I have a user using Lync 2013 and can't get logged in. I know the client works, cause I can login with my credentials. I'm trying to figure out how to get to the screen where I can change his login address (e-mail address) to match his LAN ID, but for the life of me I can't find any articles showing how to do that. I've deleted his SID folder and removed his endpoint file, but it still won't prompt to change his login info.  If anyone has any idea on how I can get to the screen to match his LAN ID with his e-mail address at the login screen, I would very much appreciate it.  Thanks!

Hello Jim,

You can change your sign-in address.

Open Lync 2013 > tools > Options > Personal (Sign-in address) and type correct sign-in address of affected user. refer below screenshot.

If issue persist then delete my sign-in information to clean Lync profile and then it will prompt you for credential. Refer below screenshot.

Regards'

Balu