Google announced they are turning off access to their unsupported Autocomplete API on August 10, 2015.
The reason? Google said some of you may think i tis useful but the "overall the content of our automatic completions are optimized and intended to be used in conjunction with web search results, and outside of the context of a web search don’t provide a meaningful user benefit." So not useful.
Either way, they are Google APIs and Google can do what they want with it.
As Wissam said on Google+, this can be a big slap to keyword tools and SEM tools in general. Many tools do use the API to come up with keyword ideas. Without that API, they may need to think of other ways to handle that.
Forum discussion at Google+.
