I just experienced the same problem and was able to fix it.
This is going to sound stupid,
but it stop the instance and start it again
on the instance page.
and the google cloud ssh window works again.'
No access from console SSH, it's completely google managed and they should have the free answer as it's a problem on their side instead of dumping to offsite Q&A as a policy.
I did have also have an error 13 for a while, simply trying to open the window again and again. If it wasn't that they hosted dot.llc and AWS wasn't, I'd be on the less user-friendly but more stable AWS.
IF this doesn't work I think the solution is to attach the volume to another instance, basically redoing all the network, IP, DNS, etc. either that or reload all the YUM instances and pull from a back-up. This is a severe approach though, have some instances backed up, I hope I never need to use them. Looks confusing.
Simply intolerable, where I come from it's firing someone if a production server is down and the answer is "We'll get back to you in 24-hours." or the hundred bucks.
But the turn it off and on again works on the cloud (shudders)
That it'd go down in the first place is bad. I've never ever had to turn off a linux server and back on again to fix something before.