What I meant with the priority by geolocation is actually "country restriction" =) sorry about that.
Anyway, I just found out why the stock was always showing "out of stock" although I was doing everything right. When I tested the front-end in an incognito window I saw the stock of the inventory of my country showing properly.
So it seems like the country recognition wasn't working properly only when I'm logged-in to the admin account. I went into my admin profile and found no country set in the shipping address. When I set it to my country the stock showed properly on the front-end.
I guess this is a minor bug, because the plugin gives priority to the country set in the account shipping address, but when there is no country set, it didn't detect the country by geolocation like it does in the incognito window (logged-out state).