Go to notifications>Advanced(top right corner)>Messages app>New messages>then under sound I had a number, so I clicked on it and picked the notifications tone I wanted and backed out of all that and it fixed the problem. I hope this helps.
Only found where you select the tune with a dot but this selected tune works the same for every contact you have. Previously could select tunes individualy for each contact therefore know who sent it before you looked. Not happening now ????