As Euro has explained the chances of selection are the same over a region. The selection is random and there is nothing that stipulates a country has to receive at least one selectee.
So - if the chance of selection is 1 in 100 (for illustration) - and one country has 100,000 entries you would expect them to get 1000 winners - right. Now, another country in the same region has 200 entries. Statistically, they should get 2 winners - BUT because it is a random process and a small number of entries they might get 4 winners or none. That is the nature of a lottery process.
Not convinced?
OK - lets look at 2015 numbers (where we have entry and selectee numbers).
Antigua & Barbuda had 349 entries (plus 299 family). The got 6 selectees (including family). Let's assume that is 3 winners and 3 family (based on their derivative rate) . So - 3 winners from 349 - that is a selection rate of 0.86%.
Argentina in the same year had 5819 entries (plus 6335 family). The got 109 selectees (including family). At their derivative rate that should be 52 winners. 52 out of 5819 - that is a selection rate of 0.89%.
If we applied the 0.89 to the 349 entries from Antigua & Barbuda we would have expected 3.1 winners.
So - where is the disqualifying element?
Now, as the overall selectee number was reduced this year, the winning chances went down. Entries from some countries might be higher or lower. But with the low number of entries and with a lower winning chance, it is not a surprise that some countries got no winners at all.