All you have to do is list out all the things you want to say, and the answer becomes clear:

"My photos" v. "Your photos": both seem to work

"We weren't able to complete your request" v. "Someone else wasn't able to complete my request."

"Please enter your valid email address" v. "Please enter my valid email address"

"To (...), you need to upgrade to a Pro Plan" v. "To (...), I need to upgrade to a Pro Plan."

The user is the second person, because sometimes your app or company needs to speak to them using the first person.