I want to upgrade Mental Case, but it does not appear in the Updates list.
Some older versions of Mental Case are no longer available for sale via the iTunes App Store. When an app is removed from sale, it no longer appears in the Updates list of the App Store app.
Even though a not-for-sale app does not appear in the Updates list, you can still update it if you haven't got the latest version. You can also install the app on a new device, provided you bought it before it was removed from sale.
To download or update a copy of Mental Case app that is no longer for sale, go into the Updates tab in the App Store app. Tap on Purchased at the top of the list, and scroll down to locate the Mental Case app. Tap the install button on the right to download.
Studies for macOS and iOS
Mental Case for Mac OS X
Mental Case for iOS