Singularity is offline in preparation for the Mac native client test tomorrow, as best I can tell.
Edit: I have asked CCP to validate this in the EVE Online to go native on macOS! thread with @ CCP_Caffeine; hope to see confirmation soon!
Edit 2: This might actually be a stress response from the servers from high volume connections - after a couple tries, I was able to get connected. Maybe give it another go? It may be throttling connections if a lot of people are logging on today in prep for the testing.