I solved the problem, but hope this answer stays here if anyone has a similar issue. The rubber grommets that hold the RAM can detach an individual bracket. When I opened it back up, the left side grommet was loose, and the back left bracket was in the open position—meaning the RAM wasn’t properly seated. Regardless, be slow and gentle when doing anything inside the new Mac Mini. I broke my antenna socket when prying it up. Thankfully I’m not worried about using it.