Administrator is not able to change user’s picture in User Profile in SharePoint Admin Center
For some users Admin is able to change picture by going to User Profile -> Manage user profile option. But for some users , Admin is not able to change pictures & SharePoint is showing the message “Only user can change this photo”. Admin can delete the photo but can’t upload.
Here is the way to change user’s picture. Just go to Manage User Profile option form SharePoint Admin Center -> User Profile and search for the user. Now modify the user & search for the property “Picture Exchange Sync State”. You will see that it’s value is non zero.
Just change it to Zero (0) & save it. Now reopen this profile again. You will see the option to update the image.