As others are saying, you need to drop the bead of the tyre down into the central well of the rim, if it's on the shoulder it'll be too tight to get off.
the new tubless ready schwalbes seem to be incredibly tight, had a total nightmare with rocket rons and nobby nics on crests yesterday.
In contrast, I just got some new tubeless ready Schwalbes (Hans Dampfs), put them onto my Crests this weekend and it was easily the most painless tubeless tyre fitting I've ever experienced. It took about a minute to get them on each wheel without levers, straight from the box, so I didn't need to leave them to sit with a tube in first, and they both went up straight off using just a track pump, without any sealant or anything (I put some in later though, obviously). It was genuinely quicker and simpler than using an inner tube, even. Marvellous.
Only problem is I keep wondering what's going to go wrong to redress the karmic balance, running tubeless isn't meant to be that easy...