Simple app, but not available on GooglePlay for some smartphones

I finished a few apps in AI Classic and AI2 already and uploaded them to GoogePlay.
Some of my friends "complain" those apps are not listed on their smartphones, when they want to download them.
They are (I think) not too complicated apps with not too much requirements.
Here is one of them: https://play.google.com/store/apps/details?id=appinventor.ai_digimuhely.SP_kalkulator

E.g. one of the phone was a Samsung ACE Duos

Do you have any idea what should I do differently to make these apps available for more people?