If she went in it initially without any challenges and now she won't, something may have happened while you were not home and she was in the crate. This might be getting a foot or toe caught or something similar. It sounds as though you are going to have to start over with her and you might want to consider trying a different type of crate. If you have a metal fold-down type crate, you might want to consider switching to a large plastic crate (such as a Vari-Kennel or airline style).
I would also play with her around the crate and do as the others have suggested, feeding her in the crate with the door open and tossing treats and toys in to the crate for fun.
Does she have anything that she just absolutely loves like a high value treat or toy? If so, you might try putting that in the crate and just letting her go in and out on her own. Wrestling with her will only make it worse, athough I do understand that she needs to go in. Please keep us posted as to what success you have.
Sabra - female GSD - born April 30, 2012
Sargeant - rescued senior GSD male/foster failure - approximately ten years old (August 2013)
Max - rescued GSD - Dec 22, 2010 to March 7, 2012 - at the bridge
Sable - rescued GSD - at the bridge