Unknown Error when trying to download an app I own on a different device

I downloaded the full app of “stop motion” on an iPhone in our home. I then went to download it on another and after signing in after clicking purchase it said “someone in your family already bought this app. You get it for free”. I then clicked ok and moments later an error came up saying “purchase failed. Please try again later. An unknown error occurred (CAStoreView@150)

we have no outstanding payments and in settings all downloads etc are set to “allow”