Online traders are weird. I used to buy and sell games online, and tcg traders don't seem any different.
They'll post a list of stuff they want on their forum, I make an offer with most of the stuff on their list and a couple things I want, and they're just like, "sorry, but thanks for the offer".
Do you even want the stuff you asked for? How am I supposed to know what's satisfactory for you if you're never willing to haggle or communicate? In real life people just usually say "it's a fair trade, but I don't want to get rid of these legacy items right now" or whatever, then I look for other things I want. After a couple exchanges, we agree and everyone's happy. But for whatever reason online traders are much more likely to flake out after asking for stuff. If someone else made an offer just say so.
I offered a dude a bunch of the stuff he's looking for for his MP Force of Will, and he just declines then goes back to his forum thread and bumps it with no changes so I assume he didn't get the cards from someone else. Why even go through the trouble of making lists like that if you aren't going to communicate with the people actually offering you the cards you want?