The web client version of the Play Store seems to have an odd bug.
For some reason, many games are currently incompatible with all devices in the Play Store web version, though the mobile app variant still works fine. This was initially discovered on Reddit and reported by Android Police.
Games like Alien: Blackout, iMonster Pro, Asphalt 9, Monster Hunter Stories and more are all incompatible through the web client. Even games that the user has already downloaded will still show as incompatible.
Downloading games via the web version lets users pick which device to download without actually having the specific smartphone in hand.
As previously mentioned, this will only affect the Play Store through the web client, so if you usually only download games via your smartphone or tablet, you may never notice this bug.
Source: Reddit Via Android Police