The Republic of Armenia was declared in 1990 so I hope this doesn't break the 20 year rule. I noticed on the Wikipedia list that it claims Pakistan doesn't recognise Armenia, is this a mistake or is there an actual reason?
Armenia and Azerbaijan were involved in a short but brutal war over the Nagorno-Karabakh enclave, and although a ceasefire was declared the conflict isn't resolved and there's still a lot of bad blood between the two countries, including sporadic outbreaks of fighting along the ceasefire line. Largely due to Islamic solidarity many Middle Eastern countries took sides in the conflict. Pakistan's position is that they will not recognise Armenia as long as Armenia continues to occupy Azerbaijani territory.
[Here] (http://news.day.az/politics/314954.html) is an interview with Pakistan's ambassador in Baku to that effect (google translate gives a decent overview).
because of karabakh conflict. you can find some information http://soz6.com/nedir/2139/pakistan