App Store Issue with Slow Shutter Cam app

I have an iPhone 5s and went to update the app Slow Shutter Cam today. The app refused to update so I uninstalled it and went to reinstall it. However, the app would not install and kept telling me I had to update it and the App Store kept telling me that I had an update, which I did not.I reset all settings, hard reset the device, signed in and out of my itunes account on the phone and the app would still not install or update and the App Store kept saying the update existed on the icon. I plugged my phone into my computer and downloaded the app from there. The App Store icon still showed that I had an update for the app and under available updates, the button next to Slow Shutter Cam said "Open" not "Update." I have been working to try to figure this out for quite some time now. I'm not sure if it's the app or my iPhone. My iPad Mini updated apps without any problems and I could install other apps without any problems. I'm guessing it could be the app, but it installed fine from iTunes but like I said early, the App Store insisted there is an update. I contacted the maker of the app but I have yet to hear back from them. I don't want to totally reset everything on my device if I can avoid it.

Any suggestions/solutions?