iCloud storage photos

honestly follow the steps in https://support.apple.com/en-ca/HT209453

if it still isn't working try power cycling your device

if it still does not work you may need to turn off and back on icloud photo library

just an fyi when toggling icloud photo library you should not experience data loss but to be sure make sure to back up your device.

also if the photos that are not uploading were sync'd from a computer they will not sync to icloud

As per this article https://support.apple.com/en-in/HT204570

If you have Optimize Storage turned on, you might not have all of your original photos and videos on your device. To download the original photos and videos on your iOS device, go to Settings > [your name] > iCloud > Photos and select Download and Keep Originals.

Make sure what is the correct format of photos that you have uploaded see this article https://support.apple.com/en-us/HT207022

And also as per this article https://support.apple.com/en-in/HT204264

if you turn on Download Originals, iCloud Photos keeps your original, full-resolution photos and videos in iCloud and on your device.

Make sure the videos length time is 5 minutes see this article https://support.apple.com/en-in/HT207587

Network speed also has a major role to sync photos .

fyi when toggling icloud photo library you should not experience data loss but to be sure make sure to back up your device.

But they will experience significant delays in knowing this has worked. With that amount of video, this re-sync will take significant time to complete.

Howe long have you waited? Have you interrupted the process in any way?

For example, leaving a wifi zone etc.

Is it possible those items are corrupt?

That is a very large library.