Old (Icloud?) photos wont load

Hello, i recently upgraded my iPad iCloud storage space and began syncing my photos for storage. I'm not entirely sure how it works, but i have encountered a problem where my old photos wont load and are unable to be sent to anyone or posted anywhere. I have quite a lot of general storage space as well as iCloud storage space, so why is this happening?

There is a small button in the bottom left of the images that has an exclamation point on it. When you press it, a notification pops up, seemingly an explanation.

Im german, so the notification roughly translates to

"Photo cannot be loaded

An error occurred while loading a higher quality version of the photo."

What can i do to fix this and be able to send my older photos to others? New photos work and send just fine.

[Edited by Moderator]