Hello Samadams1983,
We see your photos are appearing a black thumbnails and understand wanting to get this resolved. We'd be happy to assist with this.
Are you using more than one device with iCloud Photos? If so, are you experiencing this issue with all of your devices? If the answer to both questions is yes, let's be sure Dark Mode is disabled. Once disabled, let's have you select a few thumbnails, tap on the Edit button, apply an edit, and confirm it either remains black or if the thumbnail appears as it should. Also, we'd recommend to navigate to the iCloud site and confirm you're seeing the same in Photos.
If the issue continues, we'd recommend connecting with Apple Support. Depending on your region, you may be able to reach them here: Get Support
Thanks for using Apple Support Communities. Have a good one!/