Error loading higher quality video on iPhone with sufficient storage

I see you have an iPad. So, can you tell us a bit more?

• Are you using iCloud Photos to synchronize your devices?
• Do you have “Optimize Storage” checked in Photos’ Settings
• What does your iPad's Photos say under the Apple ID icon? Like this"

• Do you see all your iPad's pictures at iCloud.com?
• Have you checked to see if the Apple Account is really really the same on the Mac and on the iPhone and at iCloud.com?
• Do you have more than 10% free storage on your iPad?
• Do you have more than 10% free storage on your iCloud account?
• Has this problem always existed, or did it just start? Can you think of anything that changed that might affect your device?

What kind of iPhone do you have that has 2TB of storage? How are you trying to upload a video to the phone?