\cellcolor removes \hline
As you can read in the comments there never was a problem with the tex code. The only problem was the pdf viewer. When zooming in the lines gets visible again. This will not be a problem when printing the page.
As you can read in the comments there never was a problem with the tex code. The only problem was the pdf viewer. When zooming in the lines gets visible again. This will not be a problem when printing the page.