<human>: Can you give me the gist of the text in a nutshell?

Hi everyone! I'm posting on mobile so please forgive any typos. 

So my husband and I have been friends with these 2 married couples over the last 6 months. One of the couples is Rory and Ariel (20s) and the other is Erica and Nolan (20s). Erica and Nolan have been married for about a year and a half, and Nolan and Rory attend the same college as my husband. 

A bit of background about Nolan. He's a pretty nervous guy, and doesn't really like social engagements. He really likes to keep to himself or have very small group get togethers. He's also not doing well in school, and may go home after this semester (and taking his wife along with him of course). Erica is very sweet, and has a steady job. I really like her and think she's pretty great.

At first, we were going to each other's houses a lot; dinners, movie nights, bbqs...all in all enjoying each other's company and having lots of fun. Then, about 2 months ago, all of us couples were attending a school function together. To make a long story short, Ariel and Nolan had an extremely minor (and accidental) altercation, and neither Rory and Ariel, or me and my husband have seen much of Erica and Nolan since. Nearly every social event, any attempt to catch up with them, or plans to do with them have fallen through or they cancel last minute. 

At this point, I'm just about done trying to invite them to do things. It's frustrating to constantly getting turned down, and I can't really get them to say if there's anything wrong. I just need help trying to see if I can make the friendship work, or just move on.
<bot>: I'm friends with a couple who's not seeming to make the effort to be friends. However, I think there's an underlying issue. What should I do?