Several things to try:
Have you restarted your device? That sometimes clears up odd issues.
If an app on your iPhone or iPad stops responding, closes unexpectedly, or won’t open, click here --> https://support.apple.com/HT201398
Redownload apps, music, movies, TV shows, and books from the iTunes Store, iBooks Store, and App Store - https://support.apple.com/HT201272
How to contact an app developer - https://support.apple.com/HT207959 - for problems running an app or problems restoring purchases
If you still have problems click here --> https://support.apple.com/choose-country-region/Select your country, then a product.
Note that not all apps get rigrorous testing on all iOS versions and I have several that are quite "buggy" on my older iOS even though the developer says they should work fine and releases them for that iOS.