One of the worst things to happen to your company website is if it goes down, there is no website there when your visitors arrive at your website address, either by finding it on a search engine or a recent promotion or returning visitor.
The thing is, if your site is down for a few hours, or even a day or two, that will not affect your rankings, but being down much longer than this can have a real impact so make sure you are using a top quality web hosting service to insure against this happening.
Google will come back to check your site, sometimes within 24 hours to check it again, if your still down then they will return again but if you are with a host that keeps letting you down then its time to move your online business somewhere else.
On occasion the actual Google bot itself has been known to have problems reporting back but this is not very often, although Googlebot normally provides “pretty good reliability,” however.
At the end of the day, Google, and indeed all the other search engines, do not want to send their searchers to a website that is just not there, what would be the point, this would look bad on them if they send you to a site that was down, an unrewarding experience and that’s not what anyone wants at all.