I'm not getting notifications from only one contact I was getting all notifications from one contact but all of a sudden it just stopped giving me notifications.

Also it automatically opens the text and it doesnt say that I have read the message but read receipts are on. "Hide notifications" is turned off too.

I have an iPhone 8 Plus.
Exact same thing has happened to me - I've tried everything, and my most frequented contact will not notify, and all imessage texts come in as if they've already been opened. 

In most cases - this is a result of "Hide Alerts" turned off for that contact.