So, I'm already aware that your Retainer's class won't level up beyond your own character's level in that class, which would make sense why my lvl 1 Marauder Retainer didn't level up after running a hunting and an exploration venture (though I would've thought that she would've at least gained experience, but ok). My second retainer, however is an archer, and my main character's archer level is lvl 3, and my archer retainer didn't gain any experience either after running a hunt venture and a field exploration venture.

I tried contacting SE customer service twice, super unhelpful. Even the link they provide in their customer service response is to post on the forums leads to a "page not found". Horrible customer service - if someone sends your customer service an email request for help, at last pretend to try and help, don't confuse them by sending broken links.

Someone on another post said that devs on the forums will ask for as many details as possible, such as which mission, time, etc. I believe this was the day after 2.2 rolled out, Leviathan server. I also changed their classes (decided I wanted the Mi'qote to be the archer after all), and cancelled that one's venture in progress so I could change her character class. The only items they have equipped are the lvl 1 weapons for each class.