Contact names are gone, but still shown in Messages
Try these possible fixes :


Settings > Mail, Contacts, Calendars > iCloud > toggle Contacts on and off


The Second fix only applies if you have multiple email accounts synced with your iPhone (iCloud,Gmail etc) :


Settings > Mail, Contacts, Calendars > Gmail or whichever you use > toggle Contacts on and off 


Also check the Default Account in Settings to see which email account is selected.