After talking to a few of the crew members I quickly learned what I've been doing wrong.🥴 I brought the wrong cable to connect my Roku to the TV. It should have been a USB, not a HDMI cable. I disconnected it from my TV at home and didn't think about switching cables.
Anyway, connecting a hard drive directly to the LG TV works just fine once the drive loads all the files and you switch ine input.
btw- the movies this cruise have all been replaced with old Christmas movies and kid movies. NOTHING recent.
Even Top Gun was only shown on MUTS and not in the cabin.