Your iPhone may be taking the videos in the new space saving HEVC format.
In that case set the settings on the iPhone so, that the videos will be converted, when you download them from the iPhone, see: Using HEIF or HEVC media on Apple devices - Apple Support
In this section you’ll learn how to download photos from iPhone to computer (Mac) using iCloud Photo Library. To sync the Photos apps on your iPhone and Mac, enable iCloud Photo Library on both devices. On your iPhone, go to Settings your name iCloud Photos. Switch on iCloud Photo Library to ensure your photos get stored in iCloud. However, you don’t have to disable HEIF on your iPhone to make these photos more compatible. On your iPhone, head to Settings Photos, scroll down, and then tap “Automatic” under Transfer to Mac or PC. Your iPhone automatically converts the photos to.JPEG files when you import them to a PC. Download photos from iPhone to Mac using the iPhone’s charger cable Copy photos from iPhone to Mac wirelessly (without a cable) Once you’ve explored the different ways to transfer photos, you can decide which method works best for you. Importing iPhone photos to Mac is easy most of the time. You use a USB cable to plug your iPhone into the Mac computer, then open the Photos app on Mac, find your iPhone and click Import to get the iPhone photos on Mac. However, sometimes you just can't import photos from iPhone to Mac.
Importing this media via USB
When you import HEIF or HEVC media from an attached iOS device to Photos, Image Capture, or a PC, the media might be converted to JPEG or H.264.
You can change this import behavior in iOS 11. Go to Settings > Photos. In the 'Transfer to Mac or PC' section, tap Keep Originals to prevent the media from being converted when importing.
So disable 'Settings > Photos > Transfer to Mac or PC > Keep Originals'.
Sync Photos From Iphone To Mac
Cannot Download Photos From Iphone To Macbook
Though capturing in HEIF and HEVC format is recommended, you can capture media using older formats that are more broadly compatible with other operating systems and devices:
Cannot Download Iphone Photos To Macbook
- In iOS 11, go to Settings > Camera.
- Tap Formats.
- Tap Most Compatible. This setting is available only on devices that can capture media in HEIF or HEVC format.
- All new photos and videos will now use JPEG or H.264 format. To return to using the space-saving HEIF and HEVC formats, choose High Efficiency.