I've Reset-sync from My Google Dashboard. 
Now I'm not able to re-sync my browser.

After signing-in to my Chrome Browser, When I click on "Set-up Sync now" a pop up appears for a second and disappears,

Request someone to help me to fix this issue... 

If possible could you please try signing in to other devices with the same account or if possible could you attach the screen-cast of the pop-up that appears when you try Sync'ing.

I tried signing in with 4 desktops (archlinux/debian/mint/windows 7) and mobile (android) device with no luck, same error.
I can't change my passphrase either, when i go to Google Dashboard I get the message: "Your account seems to be empty. To start using sync, sign into your Chrome browser".
The issue seems being related to “Also clear your history, bookmarks, settings, and other chrome data stored on this device.” check option. 
Unfortunately I checked that option on my devices/desktops while disconnecting my google account and since then I couldn't connect to any of your sync servers anymore for syncing. I can sign in my account regularly but I'm not able to sync anything, it's like a "connection refused".
what i get in sync settings is "Sync has been stopped via the Google Dashboard." Sync works if signing in with another account.

Attache is my "chrome://sync-internals/"

Please help.
regards,
Giuseppe.

Deleted: aa 9.5 KB

aa 9.5 KB View Download

Thank you for providing more feedback. Adding requester "ajha@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

Problem solved, after numerous complaints on google groups, I was finally and magically abled to connect to google sync server.
Regards,

Giuseppe. 

UPDATE.

Same problem again. 
"Sync has been stopped via the Google Dashboard." can't sync anything right now.

What's going on with google servers?

Thanks for reporting this.

Looks like the server is hitting an error. From chrome://sync-internals:
Server Connection	server error since giovedì 12 maggio 2016 11:22:18

Digging into the server logs, it looks like you're client is receiving 429 responses, which imply it's performing too many sync requests. Gonna take a closer look at why the client seems to be making so many requests.

Hi, and thanks for replying.
I have a big bookmarks file (2.6mb) with more than 1400 bookmarks.
Unfortunately I wasn't able to sync them to all my devices and after a while I got the sync error. I even tried to reset sync from the dashboard and then tried syncing bookmarks again with no luck. I could sync half of all my bookmarks then syncing stop working. I've been encountering this problem for 3 days now.
What's wrong?
Regards,
Giuseppe.

Trying syncing again right now, getting another error:

“Failed to start up the sync backend.  Please make sure your network connection is working and if the problem persists please sign up and sign in again to refresh your credentials”.

Giuseppe.

How many devices do you have syncing (or attempting to sync)?

I had 2 Linuxes (one chrome one chromium) with empty bookmarks and win 7 with everything.
Now I am on my archlinux desktop I'll like to start from here as soon as I can connect to google sync server.
I'll sync one device at a time.

Everything solved finally.
This morning I manged to connect back to google sync server. I had to sign out and the relogin to my google account multiple times in order to sync all my bookmarks (5.164) on the server, I think because there are many of them indeed.
I could also monitor everything from the sync-internals page and had to wait until "bookmarks" under "Type Info" section turned green instead of yellow showing "Active: GROUP_UI" and not "Throttled".
Thanks for your support.
Kind regards,

Giuseppe.

Got it, glad it worked out. I'll go ahead and close the bug.

One thing we can do better here is to support resuming downloading of datatypes on first time sync, which we do not today due to some legacy protocol issues. As such, every time you restart, we're forcing the download to start from scratch. That's something we'd like to fix in the future that I think would help here.

Yes, that would be very useful and healthy for your sync servers. It should also avoid duplicates between bookmarks. BTW, many users are experiencing  the same problems about syncing. Fortunately I use to export my bookmarks once in a while, so I was able to save everything, only lost extensions. 
Giuseppe.  

Again. Doh!

Local State
Server Connection	server error since venerdì 13 maggio 2016 20:38:18

Passwords	Error: ModelAssociationDone@../../components/sync_driver/model_association_manager.cc:406, datatype error was encountered: Association timed out.	0	0
Autofill Profiles	Error: ModelAssociationDone@../../components/sync_driver/model_association_manager.cc:406, datatype error was encountered: Association timed out.	0	0
Autofill	Error: ModelAssociationDone@../../components/sync_driver/model_association_manager.cc:406, datatype error was encountered: Association timed out.	0	0
Autofill Wallet	Error: ModelAssociationDone@../../components/sync_driver/model_association_manager.cc:406, datatype error was encountered: Association timed out.	0	0
Autofill Wallet Metadata	Error: ModelAssociationDone@../../components/sync_driver/model_association_manager.cc:406, datatype error was encountered: Association timed out.	0	0

Hmm, that's probably unrelated to the issues you were hitting with the server. That implies something is going on with your client. Do you have a lot of saved passwords as well? I also wonder if, given the massive amount of bookmarks you have, memory you're hitting memory issues (lots of swapping) that's making the association for those datatypes take too long, although our timeout is 5 minutes, which should be more than enough.

Not really, I don't usually save my passwords.
Anyway, everything seemed working smoothly until I signed in with my mobile android device. Syncing had been successfully completed before. I also added "User-Agent Switcher for Google Chrome", do you think that this extension might create problems with syncing?
I do not have any memory issues on any Desktops, I'm not swapping at all. 
Attached is log file related to chrome://sync-internals/

Giuseppe

Deleted: log.txt 3.3 KB

log.txt 3.3 KB View Download

Update 7:35 pm.

Everything seems back to normal, all devices (1 android, 3 linuxes and 1 win 7) were synced smoothly.
Even the dashboard finally brings everything correctly.
I am sure that Google is having a lot of problems with its sync servers, many users are still complaining about problems with syncing.
Hoping this post is the end of it. Thank you zea.
Greetings,
Giuseppe.