I have the Imac middle 2011 with High Siera 10.13.6 (17G14042) so my Lightroom is an old one.
First, what version of Lightroom are you running, and is it Lightroom or Lightroom Classic.
If it's Lightroom Classic, have you used the Print module?
This should help
It's the Lightroom and its 2.4.1
That would be the cloud version of Lightroom. It does not support printing. Export the image as jpeg or tiff, then open it in Apple Preview and print from that app.