issue

So I have no idea what to do or where to turn about this issue. I have an iPhone 6s Plus with iOS 11.2.5. It was manufactured for AT&T, but it's been unlocked and I have Straight Talk service. For about a month, everything was fine. It worked perfectly. However, this month, it went from...

Root problem: most contacts on iPhone 6+ will not sync to iCloud. A few contacts sync without a problem. Newly entered contacts will not sync. Failed solutions: I have read and tried a number of solutions that are performed in Settings, as found on the Web. The good contacts: I can make a...