Can’t upload video files to iCloud.

I’m trying Tom move all my photos and videos to iCloud. They’re from various sources including an external USB drive, a QNAP NAS and a Windows 10 PC. I’m accessing both the external USB and the NAS from my MacBook Pro 2011 model running High Sierra.

I can only upload JPEG files. Neither HEIC files nor video files (in any format) from an earlier Mac backup on the USB and NAS will upload. There are no HEIC files on my Windows machine as these are mostly older pictures and videos taken with a digital camera from about 2005.

I open Photos on my MacBook and click the upload icon. When I select and open a folder on the USB, all the HEIC files and the the video files (MOV and Mv4) are greyed out. If I click on the first file, scroll to the bottom of the list and, holding the space bar, click on the last file in the folder to select all only the JPEG files are highlighted.

On the Windows PC the outcome is similar although I can select the HEIC and video files but they won’t upload. I get a message telling only JPEG files can be uploaded. I’ve tried using both Edge and Chrome browsers to access my iCloud.com account but the result is the same.

How can I upload video files to iCloud?