Could you attach screenshots of about:signin-internals and about:sync after you get "service unavailable"error.

Basic Information
Chrome Version	51.0.2704.79 (Build 0a967bea2f0b592106657f0af87985ec6b6fe44d Linux) Ubuntu 15.10	 
New Profile Management?	On	 
Account Consistency?	Off	 
Signin Status	Not Signed In	 
Last Signin Details
Gaia Authentication Result	Successful	01/12/16, 21:45:04
RefreshToken Received	Failure	01/12/16, 21:45:04
SigninManager Started		 
SigninManager Completed		 
Access Token Details By Account
Accounts in Cookie Jar
Email Address	Gaia ID	Validity
***************	104730643940905757596	Valid
Accounts in Token Service
Accound Id
No token in Token Service.




Summary
Summary	Uninitialized
Version Info
Client Version	Chromium Linux 51.0.2704.79 (0a967bea2f0b592106657f0af87985ec6b6fe44d) unknown
Server URL	https://clients4.google.com/chrome-sync/dev
Identity
Sync Client ID	Uninitialized
Invalidator Client ID	Uninitialized
Username	
Credentials
Requested Token	n/a
Received Token	n/a
Token Request Status	OK
Next Token Request	not scheduled
Local State
Server Connection	not attempted
Last Synced	Mai
Sync First-Time Setup Complete	false
Sync Backend Initialization	Not started
Syncing	false
Network
Throttled	false
Retry time (maybe stale)	Uninitialized
Notifications Enabled	false
Encryption
Explicit Passphrase	false
Passphrase Required	false
Cryptographer Ready	false
Cryptographer Has Pending Keys	false
Encrypted Types	Uninitialized
Has Keystore Key	false
Keystore Migration Time	Uninitialized
Passphrase Type	Uninitialized
Passphrase Time	Uninitialized
Status from Last Completed Session
Sync Source	Uninitialized
GetKey Step Result	Uninitialized
Download Step Result	Uninitialized
Commit Step Result	Uninitialized
Running Totals
Notifications Received	0
Updates Downloaded	0
Tombstone Updates	0
Reflected Updates	0
Successful Commits	0
Conflicts Resolved: Client Wins	0
Conflicts Resolved: Server Wins	0
Transient Counters (this cycle)
Encryption Conflicts	0
Hierarchy Conflicts	0
Server Conflicts	0
Committed Items	0
Transient Counters (last cycle of last completed session)
Updates Downloaded	0
Committed Count	0
Entries	0
Nudge Source Counters
Server Invalidations	0
Local Changes	0
Local Refreshes	0

"Service unavailable" error is reported if during signin or access token request chrome gets unexpected response from google server. It could happen for example if proxy blocks requests returning 403 code.

Could you describe steps that lead to this error. Do you get to enter username and password in sign-in form? Do you see sync confirmation?

Looks like a sign-in issue, not a sync issue. +sign-in SWEs for triaging

As mentioned, more descriptive repro steps could help debug the issue.

Thank you for providing more feedback. Adding requester "maxbogue@chromium.org" for another review and adding "Needs-Review" label for tracking.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot

@Reporter,

As per Comment#5, Could you please reply on the same.

Thanks.

--Chrome Identity automated triaging--

This bug is Unconfirmed and has gone two weeks without any activity, so it is being closed as WontFix. Please re-open if this is still a valid and reproducible bug or feature request and mark it as Available. Please see https://goo.gl/78kbny for more details. Please remove the Services>SignIn or UI>Browser>Profiles components if this bug isn't related to Chrome Identity.

For more details visit https://www.chromium.org/issue-tracking/autotriage - Your friendly Sheriffbot