Unfortunately, there could be a number of reasons why that feed is gone. The provider of that feed may have moved, he may have decided not to provide the feed anymore, etc. A vast number of LiveATC feeds are provided by volunteers and LiveATC knows when a feed goes down. In a case like this, it will probably require another volunteer to get that ZOA feed back up.
If you or someone you know can help provide a feed, more information can be found here:
https://liveatc.net/coverage/I hope this helps.
Ron
