Hi Marnetha
Thanks for using Apple Support Communities. We understand you're running into an issue accessing Messenger. Are you referring to Facebook messenger? If so, and you're unable to download or access a third-party app, you'll want to connect with the App Developer. You can see how here: How to contact an app developer - Apple Support
If you are referring iMessage, let us know exactly what the error you are seeing says and iOS installed on your device. You can find that in Settings > General > About. We will go from there.
Thanks