I have a Lenovo A6020a40 with Android 5.1.1.
Local GMail contacts and cloud ones have always been in sync till some day ago.
Then, suddenly, without any modification on my phone and/or on the cloud, sync stopped working.
I realized something was wrong when I created some new contact on the cloud and I didn't find it on my phone.
Then I created a new local contact and there's no way I can see it on the cloud
Naturally I've gone to Settings > Accounts > Google > Gmail and checked Contacts sync is on; I've also tried to turn it off and the on again, but nothing changed: after a sync attempt I have 778 local contacts and 777 cloud ones.
I've also tried Contacts Sync Fix app (as suggested on some forum), but app says none of my 778 contacts are having problems.
I'm out of ideas...
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After a few days and some brand new account created on my phone (and saved in my GMAIL profile according to my phone), GMail contacts are still 777.
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Contacts are not in sync anymore, even if everytime I change something I see my phone trying to sync.
If I change/add something on the cloud contacts, modification is not sent to my phone and vice-versa.
Note that emails and calendar are synchronized properly!