Unfortunately some of Google API servers such as GDrive and service that is used to wake and contact Android device experiences an outage.
Since our AntiTheft server requires Google to provide an initial communication link to the device (wake the AntiTheft program in the device to start communicating with our backend), you were experiencing this issue. It seems to be up and running well now.
Generally regarding the 305 - Service not available issue - we understand how annoying it is and we have changed the behaviour (we are finalising testing and it should be out next week). Since there is quite a maze of Avast and other 3rd party services that my.avast.com need to fully function, it is very prone to this type of errors. However when one of the services is down does not mean, that you can not work with my.avast.com at all. So we pushed the severity of this error to each view. It is also automatically testing the state of the service and once the service starts running, it will auto-update itself.