App store ask to pay again

Which oneSafe application have you purchased recently: oneSafe for Mac? for iOS? for Android?
If you purchased oneSafe for iOS on a first iOS device, you are supposed to be allowed to install it for free on up to 5 iOS devices using the same Apple Id.

If it's not the case, then we advise you to contact the Apple store explaining that you already purchased the app on another iOS device, specifying which Apple Id you used: they may be able to solve your problem.