iPhone Photos App Stopped Recognizing Faces in Old Photos for One Specific Person

Hello,

I have an iPhone with only over 40,000 photos and videos. I've been using the Photos app to tag faces, and it has consistently recognized and tagged all faces, including those of my daughter, until recently.

The problem I'm encountering is that the Photos app suddenly stopped recognizing my daughter's faces in old photos. These photos were previously recognized and tagged by the app, and they are not newly imported. The photos have been on my phone for a long time.

However, the app can still recognize her face in new photos.

Currently, the Photos app doesn't recognize her face in any of the old photos, and they no longer have tags. Additionally, I cannot manually tag her face in these photos either.

Could you please provide any suggestions or solutions to resolve this issue?

Thank you in advance for your assistance.