Emoji won't work on my 5s!

I have had this phone for about 4 months and until very recently my emoji app worked fine. However, if I use a emoji it just exists out of whatever app I am on. I tried taking the keyboard off and turning my phone off and applying the keyboard again, I tried completely deleting it but I have no idea how to to re-install. Any other app I try to use doesn't work. Please can somebody give me some advice about this?