No appointment date at all??

Its been 2 months i am trying to get a visa appointment date for Netherlands from algiers to visit my sister that i didn't see since 3 years, but the site is saying " There are no open seats available for selected center - Netherlands Visa Application Center, Algiers". I called the number and they tell me they are having technical issue, the problem is that the appointments are sold by some particular people !!! So why im not able to get an appointment myself !!