Unable to buy a new Pro license

[Filemon]

I am a new Enpass user. I have installed it on my Mac and it works very well. Then I have tried to install the pro version on my iPhone but the system does not let me do it. In the App Store only the basic version appears, which is installed without problem, but the Pro version does not appear. Therefore I have tried to switch to the pro version from the basic one. When doing it the system returns an error message saying that it is not allowed to make purchases from the application.
The forums indicate that in order to restore the Pro version, I’ll need to reinstall Enpass app with the same iOS Account with which I purchased it earlier. This solution does not work because it is the first time I install Enpass. Please, let me know how I can install the Pro version on my iPhone.