How do I change the permission to allow access to photos on my iPhone?

Update your iPhone to iOS 15.6.1; to current.

Ensure your iCloud Reminders app data is updated:

Upgrading the Reminders app in iOS 13 or later - Apple Support

With all reminders in iCloud or stored on some other server, try deleting Reminders app, force-restart the iPhone, and re-download the Reminders app from the App Store.

Force restart iPhone - Apple Support

Delete built-in Apple apps from the Home Screen on your iOS 14 or later or iPadOS device or Apple Watch - Apple Support

Last two steps are disabling iCloud Reminders iSettings > iCloud > iCloud > Reminders) off everywhere, wait a few minutes, restarting everywhere, and re-enabling Reminders via iCloud. this is the closest available option to an iCloud reset.

If that fails, a backup, reset, and reload.

Past that, see if Apple can sort this.

check this answer provided by community specialist:

>>Why can’t I add photo and flag to my remi… - Apple Community

>>Can’t add pictures to reminders - Apple Community

Bake4fam wrote:

It does not. There is a blank space underneath the words where the picture would go. The image does show at the bottom once it is opened under details.

Okay, so you can attach a photo, you just don’t see a proper thumbnail in the list of reminders shown in Reminders app?

Is the the photo you’re using roughly the same color as the background in Reminders?

I see something similar on 15.6.1 with a less-than-visible thumbnail, though with a screenshot image of a reminder, it blends in very well. If I pick a different image that doesn’t match the Reminders background, the thumbnail is far more visible.

What happens when you try to add a photo in Reminders app? (Tap the camera icon, tap Photo, does it allow adding the photo?)