Back in 2012, Google purchased Nik Software. Since then it has been updated, and even offered up for free.
But on the Nik Software page there is a new banner : https://www.google.com/nikcollection/
The Nik Collection is free and compatible with Mac OS X 10.7 through 10.10; Windows Vista, 7, 8; and Adobe Photoshop through CC 2015. We have no plans to update the Collection or add new features over time. Learn more about Nik.
(my bold and underline).
It seems the software has come to the end of its life. It is still available, but from that banner Google will no longer be actively updating the Nik plug-ins and filters.