Which programs have you used to try to open them? sometimes a different program will have no probs.
Do the Thumbnails view show ok? Or it may even be an 'ownership' problem and you have to take ownership of the files on the ext HDD
OnePlus 5 review
Alice Saey's mesmerising animation for Dutch singer Mark Lotterman
iPad Pro 10.5in (2017) review
Comment booster votre iPhone ?