What is the knife?
How did you try to sharpen it?
There are usually a few different reasons a knife will not get sharp.
1. You did not apex the edge. Color the bevel with a marker so you can see where you are removing steel and then use a magnifier to inspect the edge. With sufficient magnification, you can also see things such as a wire edge.
2. You have a wire edge on the edge
3. You blunted the edge during sharpening (like maybe you pressed too hard while stropping).
4. Probably 100 other things I did not list.
I recently upgraded my "microscope" so now I can look at the edge to see what it looks like even better than my hand held magnifiers. OK, I could do it before, but my new one provides better images. I would show you some samples, but it looks like I cannot simply upload an image here and I no longer pay to host images, I used to...