Steam is apparently experiencing a global outage:

https://steamstat.us/

I just got kicked out of a game, and now back at Steam login. 16k+ reports on down doctor.

https://downdetector.co.uk/status/steam/

I pity their support staff, for an outage like this the shift must be hell.

Connection managers started dropping about one hour ago, and up to a few minutes ago there were one or two thousand people in-game. Now it's dropped to absolute 0, eerie :)

Just shows that anything can die for any such reason. I doubt this was a rollout of some-sort.

Could have been related to them rolling back the Summer Sale storefront, which just ended in Europe about an hour ago.

Yep! I'd love to see the write-up for an event with so wide an effect.

Yes, and because I coincidentally decided to reboot before playing, I stupidly reinstalled Steam (and therefore uninstalling all my games) because the I immediately defaulted to thinking it was an issue on my end.

We're trying to queue for Deadlock, but we can't add our friends to the lobby

Yep. Didn't come up when I rebooted my machine.