I want to move the vertex in this direction[![enter image description here][1]][1]


  [1]: https://i.sstatic.net/0PtpY.png

But it won't let me. I can move it in the X and Z axis but not the Y, like the plane is stuck being 2D and won't enter the third dimension.

[<img src="https://blend-exchange.com/embedImage.png?bid=S7enye0j" />](https://blend-exchange.com/b/S7enye0j/)