Yep. Sounds like the app needs to be updated by the developer.
Also you could try a hard reset of your phone, just to make sure it's not a hang up or something, although I highly doubt it, it's worth a try. For iPhones older than the 7 and 7 plus, you hold the power and hone buttons until the Apple logo shows and then let off the keys. For an iPhone 7 or 7 plus, you use the volume down and the power button to hard reset the phone, following the same steps as above when you see the Apple logo. Hope you get it resolved. First thing I would do is to see what it says about the app in the App Store. If it needs to be updated, or if it has possibly been pulled due to it being a 32 bit app, or it not getting any updates from the developer for a long time. Again, hope you get it resolved. Good day