This is another shortened Korean phrase and it means....
Follow me on social media!
맞 (mahj) comes from the verb "to face each other"
and 팔 (pahl) comes from "follow" (pronounce pahl-low in korean)
So 맞팔하다 (mahj-pahl-ha-da) means to follow each other's accounts!
Basically its Korean for #Follow4Follow LOL!