Solution:

If you are seeing an 'http 1.1 Service Unavailable' message, your Webex website is currently being switched over to another set of servers. During this switchover, the cached DNS entries for your Webex website may be temporarily pointing to the incorrect servers.

See the bullet points below to resolve this issue:

• Close all of your web browsers, then start a new web browser and attempt to connect to the Webex website
• Clear the cache and cookies of your web browse:
  • Mozilla Firefox - WBX38898 - How Do I Clear my Cache and Cookies in Mozilla Firefox?
     
• Flush the DNS cache - WBX18967 - How Do I Perform a DNS Flush from DOS Command Prompt?