I'm in the same boat, still no response. I am also a graduate student, 2.5 years of regional experience in areas of interest for NATO, almost two years of internship experience related to National Security which are relevant to NATO, and language skills of interest. However, for every person like me there's an overqualified applicant with two MAs and internships at the UN or the OSCE. Rejection in general without feedback sucks, but what could also explain the delay is COVID-19 and the cohort of interns due to September, @Fl0000. Supposedly, I heard from someone I know that the internships for Sept 2020 are in danger of being cancelled.