How to upload MP4 to IPhoto? When I drag/Drop or "upload" I get a - JPEG file accepted only.

Which system version is running on your Mac? The most recent versions of photos for Mac (Photos 5 or later) are no longer supporting all video codecs, that have been supported by older versions. See: About incompatible media in iMovie for macOS - Apple Support

• While the MP4 container format is still supported by macOS 10.15 Catalina and Photos 5 or later, some codecs for the media inside the container are no longer supported, for example 3ivx MPEG-4 or the Perian codecs.

You may need to convert the video that cannot be imported to a more compatible format.

Sometimes the reason for this error message is the location of the video. If it is stored on an external volume, check the file system format. If it is not APFS or MacOS Extended (journaled) or the format is case-sensitive, photos may not be able to find the resource forks in the mp4 container.

Hello francie8991,

This page can help out with importing videos and photos on the Mac: Overview of importing photos and videos

Import your photos and videos into your photo library so you can organize and edit them with Photos. You can import photos and videos in a variety of ways:

Using iCloud: Turn on iCloud Photo Library on your Mac and iOS devices to access your entire library automatically. Or, you can turn on My Photo Stream to import only your most recent photos. (If you use iCloud Photo Library, you don’t need to use My Photo Stream.) For more information about using iCloud, see Use iCloud Photo Library to store, share, and manage your photos in iCloud.

From cameras or mobile devices: You can connect a camera, iPhone, iPad, iPod touch, or other mobile device and import photos and videos from the device. For more information, see Import photos from a camera or phone.

From storage media: You can import photos or videos saved on a hard disk or other storage devices. For more information, see Import photos from hard disks, CDs, DVDs, and cards.

From other apps: You can also import photos and videos sent to you in an email or text message, or downloaded from Safari. For more information, see Import photos from Mail, Messages, Safari, and other apps.

Cheers.

Are you trying to import the video using iCloud? It seems iCloud.com doesn't import video. You need to use Photos on your Mac that's synced to iCloud to import videos.