theming – Entity Print PDF stying issues

How can I apply CSS styling to a PDF generated from node content?

Using the Entity Print module I am able to create PDFs from my node content.
My problem is the PDF output do not reflect the styling I am applying to it. For example, the http://localhost:85/print/pdf/node/2 is the PDF url but it is entirely deviod of my styling despite my continued efforts.

Using the TCPDF (v1) pdf engine and having followed the pertinent instructions at this link, I have the following configuration code:

In mytheme.info.yml:

entity_print:
  node:
    deal: 'oliverock/deal-pdf-styling'

And in mytheme.libraries.yml:

deal-pdf-styling:
  css:
    theme:
      css/deal.css: {}

And deal.css is quite simple:

* {
    color: red;
}

div {
    background: blue;
}

As I alluded to above, I expected that simple styling to take effect in my PDFs but it’s all just black text on a white background.
And for the longest time I assumed my code was at fault until I noticed the debug line in the instructions.

All my code is visible at http://localhost:85/print/pdf/node/2/debug but that output is not a PDF.

I would appreciate some help please.