User blog comment:Rappy 4187/Technical Update: September 7, 2015/@comment-26009167-20150909152420/@comment-24473195-20150909153649

I was told some months ago by a Wikia Community manager(Staff)  that bots will eventually have to use the new authentication (OAuth). In fact, one of the bots I ran that use "google apps scripts" stopped being able to login a couple of months ago. My guess is that is around the time they implemented some code to make login checks stricter. It is likely that the api used by google apps scripts uses a different IP every time it makes an API request (for security reasons too).

Chances are that the check they added blocks  attempts to login if the login token was obtained by a different IP.