I did a little research and it appears the app developer removed/pulled this app out of the iOS App Store some time after the last update in April 2017.
It is no longer available and I assume, no longer available for re-download, either.
See the link to the developer’s Website below.
https://appadvice.com/app/ido-notepad-diary-journal/363455392
Why the app no longer works, it maybe because the app developer may not have updated the older 32-bit code in that app to make it compatible with the new 64-bit code of iOS 11 and iOS 12.
Older 32- bit devices and 32-bit coded software do not work any longer with the new 64-bit iOS 11 and 12 and other future versions of iOS.
Apple is not responsible for what third party developers do or not do with their iOS app offerings.
And they do not have to supply any notices to users, either.
When you download or purchase and download an app, you pay for the “right to use”, NOT the right to own the app. Just like the normal users’ “Terms of Use” agreements with any other software.
The app is gone, now.