Maybe a bit late... but adding a table is a bit complicated in OpenXml.
I suggest you to embed your Html code with "<table><tr><td>" + yourHtml + "</tr></td></table>"
and lets Html2OpenXml handle the table for you
I suggest you to embed your Html code with "<table><tr><td>" + yourHtml + "</tr></td></table>"
and lets Html2OpenXml handle the table for you