Let me ask some clarifying questions to help us narrow this down:
- I don't quite follow this part: "sign-in on chromebook using password and phone". Are you signing out and in on both devices? Or what does "and phone" mean?
- After the sign-out->sign-in, is Sync not working on the Chromebook, or on the phone, or both?
- On the affected device(s), could you take screenshots of chrome://sync-internals and chrome://signin-internals and post them here?

>> - I don't quite follow this part: 
>> "sign-in on chromebook using password and phone". 
>> Are you signing out and in on both devices? [1]
>> Or what does "and phone" mean? [2]

[1]
Sign-out on Chromebook only via signout button (see Screenshot 2018-12-18 at 13.21.56.png)

[2]
"using password and phone"
since chrome os v71, when I sign in onto the chromebook, 
my phone is used as two-factor authentication. 
Just like google is using for gmail (google account) as replacement for the google authenticator.

When I upgraded from v70 to v71 I could connect my phone to my account, see screenshot (Screenshot 2018-12-18 at 13.20.43.png)

>> - After the sign-out->sign-in, 
>> is Sync not working on the Chromebook, or on the phone, or both?

It is the google sync on bookmarks and Extension sync between chrome installation on the various devices. I have the impression that the sync of the mobile bookmarks does not function. 

>> On the affected device(s), could you take screenshots of 
>> chrome://sync-internals [3] and 
>> chrome://signin-internals [4]
>> and post them here?
[3] : Screenshot 2018-12-18 at 13.44.42.png
[4] : Screenshot 2018-12-18 at 13.46.53.png

hope this helps. 

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Thank you for providing more feedback. Adding the requester to the cc list.

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

Thanks for providing these details!
There is some problem with authentication, and without that Sync cannot work. I'm guessing that the problem is somehow related to the two-factor auth with the phone, but I know little about that.

+msarda: Do you know who's responsible for the "Connected Devices" feature on ChromeOS?

My guess is that the new feature of sign-in did not include the "test-case" that the a passphrase is used that is not equal to the password.

aka. there are two layers of sign-in needed for chrome sync to work, and that is probably the reason that the sign-in is not working. But I am just a nerdy user and no dev expert :)

You mean the custom Sync passphrase? No, I don't think that's related. It doesn't matter if that's equal to your Google account password or not; they're always treated as different things.
Also in the signin-internals screenshot, you can see that all the other services that require authentication also report auth errors, so it's not just a problem with Sync.

CC+ ChromeOS folks that work on sign-in. Please take a look and triage accordingly.

Just did a powerwash of the Chromebook (dell - Chromebook 13 - 7310)
Received during setup the error that passphrase was needed.
Setup completed successful including pairing of Android phone & Chromebook.
After setup, setting passphrase was successful, 
Syncing was successful.

So work around for me in this case was a powerwash of the device.

Should I close the bug report, or is it needed for some statistics, problem-process ?

mm recall that last question.
I just did a reboot and the error message returned.
This is strange.

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I receive the same error as in the screenshots above. I have been able to resolve by disabling an installed VPN extension. I have found that other users have also resolved the issue by disabling their VPN extensions, i.e., Nord, PIA, etc.

Ah, thanks for the hint about VPN! If that extension messes with our network requests, it's maybe not so surprising that sign-in/auth things stop working.

e.a.botjes@gmail.com, do you have any extensions related to VPN or other "networky" things? If so, could you try uninstalling or disabling them?

Please refer to an older bug Reported by gre...@gabrielrichard.org, Jan 23 2017
 Issue 684031  - Sign-in Error Chrome OS could not sync your data because your account sign-in details are out of date.
see: comments 34 - 39

Google Chrome Privacy Whitepaper
Last modified: December 5, 2018 (Current as of Chrome 71.0.3578.80)

See section "Redesigned Sync and Google service settings"

In version 69, Google began rolling out a new structure for Chrome settings for a small population of users. All settings that control how Google collects data from Chrome have been moved to a new settings page titled “Sync and Google services,” combining previous settings from the “Sync” and “Privacy” section of advanced settings.

I have not been included in the "small population of users" mentioned above, so I cannot help with testing  to see if the changes or settings have any effect on the sign-in issue. Good luck.

https://www.google.com/chrome/privacy/whitepaper.html

Re #14/15: No, I don't think those settings changes are connected to this issue. A misbehaving VPN extension sounds much more likely.

treib, I would agree with you, if it were limited to just one VPN extension but as I said in comment 11 above, this issue occurs with my VPN extension, VPN.ac, Nord and Private Internet Access (PIA) as far as I know of. It may not be the settings but something having to do with Chrome sign-in and sync has changed to cause this issue.

+Devlin: It looks like in M71+, Chrome's sign-in state gets messed up if there's a VPN extension. Has anything changed on the extensions side that might be related?

msarda: Has anything changed in sign-in itself? Maybe some new security measure that would not work with VPNs?

Chrome sign-in and sync model change in M68 and M69 only affected desktop (this was not applied to ChromeOS). As this bug is for ChromeOS, I doubt it is related to those changed. Do you have similar issues on desktop?

Could this be similar to https://bugs.chromium.org/p/chromium/issues/detail?id=914672 ?

Indeed, that looks like the exact same issue! Also bug 918321 seems to be the same as well.

Are these extensions using the vpnProvider API, or the webRequest API?  If the latter, there are some changes that +karandeepb@ made regarding the permissions model.

+emaxx@ as well as owner of the vpnProvider API.

From the discussion at crbug.com/914672, it seems there was a bisect and it seems this is related to sign-in behavior. (See https://bugs.chromium.org/p/chromium/issues/detail?id=914672#c46)

Marking this as a duplicate of 914672 (per comment #23 and #21).

sorry for the late reply.
1. I only have this on chrome OS. (Chromium & Chrome on windows and ubuntu do not have this issue when I use Nordvpn extention)

2. When this occurs I can not resign-in and insert the passphrase.
I have a seperate passphrase and am not able to change that via settings.
Currently my chromebook is under repair so I can't provide any screenshots more then I have posted in the #1 post.

3. I scrolled through the 914672 and they focus on sign-in and not on "not being able to re-insert the passphrase" .. so I have the feeling this is not a duplicate.

If this only affects ChromeOS, then I agree this is probably not a duplicate (the other bug affects Windows).

May be similar to https://bugs.chromium.org/p/chromium/issues/detail?id=90540

Requesting a bisect since it seems this is not a dupe per c#25 and c#26 and is a regression.