Unfortunately, some banks are pieces of garbage and literally have no idea what they're doing, and make it almost impossible to do many regular banking features from outside their borders. This extends to their stupidity of not allowing downloads of their banking app when outside the borders. PlayStore is pretty perceptive, and even if you use a VPN you still might be blocked.
The only way I've found, although this does not seem particularly secure (thanks, irresponsible bank), is to use https://apps.evozi.com/apk-downloader/ and paste in the app domain from the PlayStore (from search) and sideload it. It will then perhaps require an update to the app, which will only complete if it can launch in PlayStore (Aurora didn't seem to work).