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 we have created a page to allow you to stay up to date with us and the availability of our system. On this page, you can directly see 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 and it will be worth checking our status page.
Please visit our Server Status page at 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, Atom Feed or E-Mail.