Table Header Cells do not have a grey background anymore

[AxelMKlein]

When I print a tiddler with the Printriver plugin now, header cells in tables do not have a grey background anymore.
This holds true for the printed pdf, the preview is still okay.
This worked previously, but does not anymore.
Of course I am not sure whether that's an issue of the Printriver-plugin.

I am using Tiddlywiki 5.2.0 and Printriver 0.2.2.

Thank you in advance