Problem with app I have developed

I am a new developer when it comes to iOS apps. Something I would like to specify is that I have an account, but I am not paying for the developer account. The app I have created is just for personal use for the time being. The code has no errors when I run it or load it onto my iPad. I do have one warning, which says "No non-expired provisioning profiles were found." It works perfectly fine, but after a few days, the app will no longer open. If I press the app icon, it just fails to load. Does anyone know of a reason for this? I do not get an error message when it crashes either. If anyone could help, that would be great. Thanks in advance.