I can’t seem to download anything from Cosmos, I tried hdri’s and models.
It also glitched for me the other day…it seemed to fix itself after some time, so maybe it was someone at Chaos unplugging their router 
Maybe, It looks to me like a cache or permission problem.
It could be I guess. I leave my pc switched on for long periods, so something may have changed…some update or whatever, to mess it up.
I rebooted and it was fixed iirc 