TeamViewer is an internet based product, and sometimes there are outages. We understand this and that this has an impact on your daily business and have created a page to allow you stay up to date with us and our availability. You can see at this page if we are having service interruptions or if there is something larger going on.
Error messages like The server did not respond or Sign in request failed might be caused by an outage.
Please visit our Server Status page status.teamviewer.com to stay up to date or to see if you're not the only one having an issue.
You will find a link to this page also in the footer of the TeamViewer Community.
Also you can subscribe to the status page as an RSS feed or Atom Feed.