Why isn't my Go SMS app receiving messages?

[Twonpidh]

I've had this app going on a year now and for some reason it stopped receiving messages. My job requires I use my phone a lot because people are always texting me so I really need help trying to figure this out. People say they keep texting me but my phone hasn't gone off and when I go into the app there isn't any new messages even though they show me on their phone that they texted me. Has anyone else experienced this same problem?? Please help!!