For years I had a gmail account set up on my iPhone (currently an iPhone 6 running IOS 9.2.1). But if I made a change to a contact or added a new one on my phone, the change never synced to my gmail contacts for that account when I accessed it on my computer. And vice-versa - if I updated a gmail contact on my computer it never synced those changes to my phone. Now it works.
NOTE: When I originally set up this gmail account on on my phone last year, I selected both mail and contacts in Settings>Mail, Contacts, Calendars section for this account.
Here are the changes I just made:
1. I went to Settings>Mail, Contacts, Calendars>Add Account>Other>Add CardDAV Account
2. A new window opened on my phone showing:
- Server - I put in "google.com" (no quotes)
- User name - I put in my full gmail address
- Password - I put in my gmail password
- Description - I put in a nickname for my account
3. Once I entered all that information correctly I saw green check-marks for each line and the window closed.
4. I then opened Contacts on my phone and saw that my contacts from that gmail account were populating on the phone. They were already on there (see NOTE above), and were populating again, creating a number of duplicates. I let the process run and waited until the new CardDAV contacts were fully populated (synced).
IMPORTANT:
5. After step 4 was complete, I went back to Settings>Mail, Contacts, Calendars for that specific gmail account and turned the Contacts slider off (from green to gray). A message popped up saying all the contacts for that gmail account would be deleted from my phone, and it asked me if I wanted to proceed. I said yes, because in step 4 all those contacts were populated to my phone via the CardDAV function for this same gmail account.
6. At that point I was in the Contacts list on my phone. In the upper left corner was a button called Groups.
7. I clicked on that button and unchecked all of the groups except for the group associated with that gmail account.
8. I went back to the contacts list and noticed the the word Groups in the upper left corner was gone, and was replaced by an "update circle" (a blue 3/4 circle with an arrow on one end).
9. At that point all of my gmail contacts were in my contacts list. The ones I had updated on my laptop were now on my phone, and the ones I updated on my phone were now on my laptop.
This whole process took about 20 minutes of trial and error because I really didn't know what I was doing. But it worked for me and I hope it works for you too! Good luck.