I'm trying to amend my tax return, because my 403b wasn't calculated into my original tax return. But everything keeps telling me I'm not eligible for this. Please help.

Was the 403B contribution not listed on the W-2 box 12 code E when you filed the original return ?   If it was then you have nothing to amend.  

On my original w2 box 12 is filled out but it didn't transfer over to turbo tax for some reason. And now it's telling me I don't have eligibility for this.