Hello,
I have an app which is available only for some countries, including France. But people living in Monaco, needs to cross country border, to be able to install. Is it possible? I was pretty sure, Monaco is included in France (as AppStore country settings), but I have no way to check this. Same for San Marino - if Italy is enabled, San Marino citizens should be able to install without leaving their country?
It is bizarre, you should contact Support.
In the meantime, if your potential users are located in Monaco, may be they could temporarily change to France for the time of download: