Some apps are not displayed on Google Play™ because your device may not meet the requirments.
For example, if you don't have GPS module on your device, any app where the developers said that a GPS module is required won't be displayed. You can see it in the All Apps section if you downloaded it for another device but it will not be possible to install it.
Developers can also choose specifically which devices are compatible with their app(s).
The only solution is to contact the developer and ask him to make your type of device compatible.
At last, make sure to have enough disk space available on your device to install the application and the related data