Thanx for pointing me to the the right place to download Lync 2010 for reinstallation.  Unfortunately reinstalling it didn't solve the real problem of my inability to log-in.  If one is the only administrator of the O365/Lync 2010 beta there seems to be no way to reset passwords.  Lots of people seem to be having this problem but I haven't seem any answers to the problem.  Any solutions or suggestions?  Lync seems like it would terrifically useful if I could get into it.

Hi DaLarry,

You need to first ensure a Lync online license is assigned to the user.

What's the error message when you fail to login Lync online? Can you login to OWA?

Have you lost the admin password?

How do I trouble shoot the Lync License issue?  My local Outlook seems to log-in with no problems to the Exchange server if that's what you mean.  I guess either I or Lync have "lost" the admin password.  That's a puzzler to me because I know what it should be; at least what I intended it to be.  I use very complex passwords and I always record them in a secure, offline place before assigning them.  I've been sort of transfixed by this Lync issue so I haven't really explored what Office 365beta can really do.  Is there anyway to reset the password?  I'm the one and only adminstrator.

I had a similar issue but i managed to sort it out it after a few try and errors. I removed Lync and all traces of it from my laptop. Rebooted and started the installation all over. This time when it was done, I clicked the Gear icon at the top right of Lync window to bring up the options menu. Clicked personal and on the right, next to where the email log in address is, clicked advanced. Chose the option button for the 'manual configuration'  In the 'internal server name or ip address' input (sipdir.online.lync.com:443) without the brackets. Alse input (sipdir.online.lync.com:443) without brackets in the external server name or ip address field. Click ok twice to get back to Lync main window.

Now this is the weird bit, instead of signing in from the Lync window, i signed in from outlook, and you can see the sign in from the lower right corner of outlook. This time when I clicked sign in, Lync popped up with sign in page, asking me to enter the user name and the password which i entered and this time i unchecked 'save password' just in case i got it wrong, but i didn't and voila, i was signed in.

Thanx!  I too got it sorted out as well but discovered my "lost credentials"!  I got busy and gave up on it for a while.  One day I went back, determined to get in and it accepted the credentials it had been rejecting??  Weird!