On the launcher, where you see Tekkit on the left. Click on the little Gear Cog underneath it and click "Set to Latest" and then save. You'll be able to get on.
No kidding. Good thing I have mining turtles. Waiting for them to mine out more diamond so I can make more crystal chests so I can put more turtles to work.
I'm making a house 23x25 from bedrock to above cloud cover with a stairwell down the middle. May find a way to rig an elevator if I don't just lay railroad tracks.