I want to sync my Google contacts on my iPhone.
When I try to add my Google account on
Settings > Contacts > Accounts > Add Account > Google, it show me the login page, but when I finish logging in it briefly (about 1 sec.) show me the page with the "Gmail" title where I can select the services to synchronize (Mail, Contacts, Calendars and Notes) and go back to the "Add Account" page without adding the account.
I have tried on several iPhone models, on Wi-Fi and on a mobile network, the problem is always the same.