Google Plus photos has been split out into a separate product, Google Photos. As part of this move there were some API changes, in particular an newly enforced requirement to use OAuth 2.0. With some help we managed to get the tool updated after a period of 1-2 weeks of downtime in late June 2015.
Usage volumes have since been steadily increasing: over the period June – December 2015 daily usage has doubled. I’m not sure whether it’s due to a decline in Flickr usage, and increase in Google Photos usage, or a combination of both (my guess). I need to spend some time working on improving the efficiency of the tool over the holiday period, but until then would ask for your patience. It’s working, it’s just a bit backlogged.