Why can't I get into the app even though I always correctly enter password and user name? Does the PS app wrong password or user name why?

So I created a PS4 account with my brother two years ago, which is now our main account, but recently my brother doesn't know the email address anymore because it was one of his school email addresses, and if I now, for example, want to log on to the tablet on the PS app with the correct username and password there, check the password and username again, although everything is 100% correct, you know whether you can get a confirmation email otherwise receive, or how to change the email, since we no longer know the old one without deleting the account, or losing any game data? 😥😥

Please for urgent help, I'm really very desperate 😥 I'm very grateful to everyone who knows a little and can help me, or experience with this problem when registering with the app 😥👨💻 ✍

Have you tried upper and lower case letters? Maybe that's because.

Thank you for your answer yes we have tried everything but still does not work, although we have written everything down, except the old email address that we just forgot, but username and password just as when logging in to the account, 😥👨💻

Look for ps4 support