I have been trying recently to access my photos from my previous IPhone 6, bu unfortunately, most of the photos could not be opened and cannot load to full quality. I was wondering why, as I am paying for iCloud.

I cannot access my photos from my iPhone, I did try to back up the phones, but nothing happened. I can see this sign ! circled and unfortunately, they are unable to be downloaded. I am paying for iCloud and never had any problems, I can still see some of the photos but most of them are unavailable. I was wondering is there any chance to recover them, as I was using the phone for over 4 years and have a lot of memories there. Thanks in advance.