I'm having a print problem since updating my Mac Sierra. Indeed photoshop does not want to make the impressions in landscape. I was on CC2017 when the problem started. So I realized the Adobe update and passed in CC2018, the problem is still there.
The print interface remains stuck in portrait mode. Even when changing to pay the impression is done vertically.
Have you experienced this problem since the Sierra update?
MacOS High Sierra 10.13.1
What printer are you using?
Have you checked for a print driver update?
What Mac hardware are you using?
Have you tried resetting Photoshop Preferences?
Have you tried reinstalling the printer driver?
Is this relevant?
I'm not a Mac user, but this will at least bump your post to the top of page one. I have also edited the subject line to make it clearer what the issue is.