Hi, I just got my Galaxy S6 a couple of weeks ago. I love the Message + app for texts. But I have noticed a problem. Certain notifications are not working for texts (even though they are assigned to a specific contact). Some of them are downloaded from a 3rd party app (like Zedge) and some are cut up MP3 files from downloaded songs in the music library. Some work and some don't, even though they are from the same source - and are all MP3 files.
But when I switch to the native Samsung Message app, those notifications DO work. So I'm assuming the issue is with the Message + app, and not the phone itself. I have tried moving files around in the device storage to make them accessible to the apps and allow me to choose them when I am assigning ringtones and message tones.
Do you have a work around for this? I would REALLLLY like to keep using the Message + app - my fave feature is the editable pics, BUT if I can't assign specific tones for specific contacts, I will have to move to the native app or worse, a 3rd party one like Chomp or Handcent. This feature is a deal breaker.
PLEASE HELP!!!! 
Thanks in advance.
Sandy