We now have a definitive answer, there was an improvement to the cloud system that renders it incompatible with older cards.
If there was truly an updated system that couldn’t be rendered correctly on older cards, that would be acceptable, but I’m very upset that they didn’t say anything in the patch or make a public announcement or refresh the minimum requirements, and instead they had us looking for the cause for several days when we really should have been notified in advance.
As for whether it really can’t be made to work on older cards, I’m having some doubts as well. Not working with Kepler maybe, but when it’s working on Maxwell 2.0 and not Maxwell 1.0 it doesn’t make a lot of sense as the two architectures are not very different. Too bad we don’t have any reports from AMD users, but it’s understandable as they haven’t been competitive with NVIDIA for several years.