Cannot Login

We are having an issue where our users can no longer login.  When they attempt to login, there presented with:

I ran into this problem when running multiple sites locally to try some things out.  This error happened when I had different users with the same email address.  I don't really understand why this would happen, since they were separate sites (though on the same server), but giving each user a distinct email address made it go away.

Hmmm... That is our scenario also, but in this case, we actually need to have multiple sites running in production.  They all actually point to the same database, but have minor differences and logic.  They also all have the appropriate licenses. 

Each of my sites have their own database, which is why I don't understand why there should be a conflict.  This is a concern if we have a staging and production site with the same users.

@Telerik... any help?

There's more info here:
http://www.sitefinity.com/devnet/forums/sitefinity-4-x/bugs-issues/login-issue.aspx
I still haven't really figured this out.  There are two items related to login, some fields in the database and a cookie on the client.  There does seem to be browser dependency -- I can't get IE8 to log off another user.  I have good luck with Firefox.

FWIW: Check the redirect_uri arg in the querystring of the login page, to see where it intends to send you once authenticated... it helped me solve a login issue with converting to V5 where we had saved '/Sitefinity/login' as the URL to login, but this has changed in V5... so on requesting the old page we'd get directed to the new authenticate page, where you would login, and then get a 404 because the login page doesn't exist... Doh!

One of the things we discovered with this issue is the URL appears to be case sensitive, so it your virtual directory is TestSite, then use something like testserver/.../
We found if we used testserver/.../ then we would get various issues like the redirect loop.

On my Windows 8 desktop FF logs in but Chrome and IE(10) have this issue. On my Windows 7 laptop all 3 work (IE9)

Hi,

What I would suggest you is to review the following Sitefinity forum where a client has the same problem. Furthermore, please go to Administration -> Settings-> Security  and check the Authentication Cookie - by defualt we are using sliding expiration and a timeout of 2 hours is set for the cookie and this is the specified value. If the problem still persist would it be possible for you to open a support ticket and send us a link to your web site and login credentials in order to investigate the problem in more depth.

Kind regards,
Stefani Tacheva
the Telerik team

For me the whole issue had to do with the date and time of the server. I logged into the box and found that the time was set to the day before. The server time had fallen back and was not updating so the cookies were sometimes expiring immediately. Updated the time and all started working.

Was happening on Sitefinity 4.4 and 5.4