I would guess one of two things. The app looks to be region restricted, meaning you can only install it if you live in a specific country. From what I can tell, this app is able to retrieve records from your providers, so being region restricted makes sense. If you are running through a VPN or proxy, that could block installation because the Play store thinks you are located elsewhere. The other possibility is that your phone simply isn't compatible.
When an app isn't able to be installed, for whatever reason, a Play Store search will not show any results for it even if it exists. I did a regular Google search, which did find the app and linked me to the Play store description. It looks to be poorly rated, but have a look and see if it'll let you install it or give a notice of why it won't.
There's also a minimum Android version required, but the OP does not indicate which device or Android version she (I can only assume based on the nature of the app) is using...