I went into the office I now work at, greeted 2 coworkers I've already worked with, they looked at me, said nothing, kept talking to themselves.
How am I supposed to interpret that?
I think you should interpret it exactly how it sounds like
It may or may not be fair. Personally, with a very few exceptions, I dislike coworkers and want few interactions with them whether positive or negative. I just don't care. But regardless of that, your coworkers are there because they have to be, and if they've decided they don't want to interact with you and are now letting you know, that is their option, whether it's fair or not.