ipad pro won't download a previously purchased app

Hi, yes I am. I have been in contact with the developers and they have advised me that there is no need to delete the Beta version before re-downloading the App Store version, as the Store version will overwrite the Beta version. This is how it has worked previously.

I have already tried that route. I initially deleted the Beta version before attempting to get the Store version, with the same result. I got the previously mentioned message. The developers resent the Beta version to me just so that I at least have a version that works.

For further information, I signed out of the App Store completely. Signed back into the UK App Store again. (This is the Store from which I purchased the App. There is a little cloud next to the App’s icon.)

When I tap the cloud to re-download the App, a message comes up asking me to enter the password for the USA App Store. This is really confusing me. According to the receipt available on my Purchased Apps, the App was purchased from the UK Store!