[BUG] gcloud not working for dev-test instances

[platfowner]

Error log:

ssh: connect to host 34.80.97.184 port 22: Operation timed out

Recommendation: To check for possible causes of SSH connectivity issues and get
recommendations, rerun the ssh command with the --troubleshoot option.

gcloud compute ssh dev-test-0 --project=testnet-dev-ground --zone=asia-east1-b --troubleshoot

Or, to investigate an IAP tunneling issue:

gcloud compute ssh dev-test-0 --project=testnet-dev-ground --zone=asia-east1-b --troubleshoot --tunnel-through-iap

ERROR: (gcloud.compute.ssh) [/usr/bin/ssh] exited with return code [255].

[platfowner]

It turned out that it was an internet provider's issue (SK Broadband). Now resolved by replacing an internet modem.

[platfowner]

ERROR: (gcloud.compute.ssh) [/usr/bin/ssh] exited with return code [255].

[platfowner]

Is turned out that 'default-allow-ssh' firewall policy has been disabled since the previous issue.
I just enabled it again, and now it works.