OzzieWoods Said:
"When playing DVD through external Apple DVD player - screen grey but Audio okay.: I have no idea what you are saying as I’m not trying to record the DVD I’m trying to watch it on my Mac, I use my Mac whilst travelling and want to watch my DVDs whilst away from home.[...]"
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Piracy seems to have been the issue. That not being the case, a few thoughts to try...
A. Google These Forums:
Start with this Google search query: grey dvd player screen site:discussions.apple.com. About 964 results pop up for me. So, add more words and see what pops up.
B. Damaged DVD Player:
If you boot in Safe Mode, you might be able to fix the Apple Library's coding, if corrupt somehow. Go here to find out how to do so: Start up your Mac in safe mode - Apple Support
C. Create a New Admin:
Try creating a new administrator, for temporary use. Do you still get this error? If not, then use that user for now. See here: Set up users, guests, and groups on Mac - Apple Suppport